Picture coding apparatus and method thereof

ABSTRACT

In a picture coding apparatus and a picture coding method, when a picture data is hierarchically coded, compression efficiency can be improved, and the deterioration of picture quality can be reduced. When a picture data is hierarchically coded by utilizing a recursive hierarchical representation, adaptive division of block is performed corresponding to the characteristic of the picture data and then coding is performed, and thus obtained hierarchical coded data is transmitted, so that the block of the lower hierarchy can be adaptively divided, thereby the information quantity such as a plane portion of picture can be reduced.

TECHNICAL FIELD

The present invention relates to a picture coding apparatus and themethod, and is suitably applicable to, for example, a picture codingapparatus that divides and codes the predetermined picture data into theplural picture data composed of different resolutions.

BACKGROUND ART

Heretofore, as this sort of picture coding apparatus, there is such adevice that hierarchically codes an input picture data using ahierarchical coding scheme such as the pyramidal coding scheme (JapanesePatent Publication No. 142836/1993). In this picture coding apparatus,the high resolution input picture data is treated as the first hierarchydata, and the second hierarchy data which has a lower resolution thanthe first hierarchy data, the third hierarchy data which has a lowerresolution than the second hierarchy data, . . . are formed sequentiallyand recursively, and these plural hierarchy data are transmitted througha transmission line which is composed of one communication channel or arecording/reproducing path.

A picture decoding device which decodes the plural hierarchy data isable to decode all of the plural hierarchy data, and also is able toselect and decode the desired one out of the hierarchy data, based onthe resolution of a corresponding television monitor and the like. Bydecoding only the desired hierarchy data out of thus hierarchized pluralhierarchy data, the desired picture data can be obtained, with theirreducible minimum of transmitting data quantity.

As shown in FIG. 1, the picture coding apparatus which realizes thishierarchical coding such as a four hierarchy coding has decimatingfilters 2, 3, 4 and interpolating filters 5, 6, 7 both for three stages,and progressively forms the compacted picture data D2, D3, D4 of whichthe resolutions are low by the decimating filters 2, 3, 4 of each stagewith respect to the input picture data D1, and returns the resolutionsof the compacted picture data D2, D3, D4 to the former resolution priorto the compaction by the use of the interpolating filters 5, 6, 7.

The output D2 to D4 of respective decimating filters 2 to 4 and theoutput D5 to D7 of the respective interpolating filters 5 to 7 areinputted into the difference circuit 8, 9, 10 respectively, hereby thedifference data D8, D9, D10 is generated. As a result, in the picturecoding apparatus 1, the data quantity of the hierarchical data isreduced and the signal power is reduced. The sizes of the differencedata D8, D9, D10 and the compacted picture data D4 are 1, 1/4, 1/16, and1/64 times the size of the input picture data D1 in area, respectively.

The difference data D8 to D10 which are obtained from the respectivedifference circuit 8 to 10 and the compacted picture data D4 which isobtained from the decimating filter 4 are compressed by respectivecoders 11, 12, 13, 14. As a result, the first, the second, the third,and the fourth hierarchy data D11, D12, D13, and D14 which havedifferent resolutions are sent out, in the stated order, from therespective coders 11, 12, 13, 14 to the transmission line.

The first to the fourth hierarchy data D11 to D14 which are transmittedin this manner are decoded by a picture decoding apparatus shown in FIG.2. The first to the fourth hierarchy data D11 to D14 are decoded bydecoders 21, 22, 23, 24 respectively. As a result, the fourth hierarchydata D24 is outputted from the decoder 24 first.

At the adding circuit 29, the output of the decoder 23 is added to theinterpolated data of the fourth hierarchy data D24 which is obtainedfrom the interpolating filter 26, hereby the third hierarchy data D23 isrestored. Similarly, at the adding circuit 30, the output of the decoder22 is added to the interpolated data of the third hierarchy data D23which is obtained from the interpolating filter 27, hereby the secondhierarchy data D22 is restored. Furthermore, at the adding circuit 31,the output of the decoder 21 is added to the interpolated data of thesecond hierarchy data D22 which is obtained from the interpolatingfilter 28, hereby the first hierarchy data D21 is restored.

In the picture coding device which realizes such a hierarchical codingmethod, the input picture data is divided into the plural hierarchy dataand coded, therefore the data quantity is inevitably increased by theamount of the hierarchy component. Consequently, there is a problem thatthe compression efficiency is lowered for the amount of the increasing,in comparison with a high efficiency coding method which does notutilize the hierarchical coding. Besides, there is a problem that in thecase where the improvement of the compression efficiency is aimed, thedeterioration of picture quality is induced, due to the quantizer whichis applied between each hierarchy data.

DISCLOSURE OF INVENTION

Considering the above points, the present invention provides a picturecoding method and a picture coding apparatus which is able to improvethe compression efficiency and is also able to reduce the deteriorationof picture quality when hierarchically coding the picture data.

To solve the above problems, in the present invention, a picture codingapparatus for coding inputted picture signal, to recursively generateplural hierarchy data each having a different resolution, comprises:determining and dividing means for determining the way of adaptivedivision of block which corresponds to the characteristic of the picturedata; and transmitting means for transmitting the hierarchically codeddata which is obtained from the determining and dividing means.Therefore, the picture data can be divided adaptively into blocks.

Further, in the present invention, a picture coding apparatus for codinginputted picture signal, to sequentially and recursively generate pluralhierarchy data each having a different resolution, comprises:determination controlling means for detecting a block activity value ofa predetermined block of each hierarchy data excepting the uppermosthierarchy data having the lowest resolution, for generating the divisiondetermination flag for determining the way of division of a block on thebasis of the block activity value, and when the determined resultshowing that the block activity value is smaller than the predeterminedthreshold value is obtained, for generating the division stop flag forstopping the division of the plurality of lower blocks which correspondto the block, and then generating the control signal for stopping thedetermination of the block activity value of the plurality of lowerblocks and the transmission of hierarchy data of the plurality of lowerblocks; and transmitting means for transmitting the determination flagof each block along with each coded hierarchy data. Therefore, thedecision flag is transmitted along with the picture data which has beendivided into blocks.

Further, in the present invention, a picture coding apparatus for codinginputted picture signal, to sequentially and recursively generate pluralhierarchy data each having a different resolution, comprises:determination controlling means for detecting the block activity valueof a predetermined block of each hierarchy data excepting the uppermosthierarchy data having the lowest resolution, for generating the divisiondetermination flag for determining the division of a block based on theblock activity value, and when the determined result showing that theblock activity value is smaller than the predetermined threshold valueis obtained, for temporarily generating the division stop flag forstopping the division of a plurality of lower blocks which correspond tothe block, and when the determined result showing that the blockactivity value of at least one of the plurality of lower blocks isgreater than or equal to the predetermined threshold value is obtained,for changing the division stop flag to the division continue flag forcontinuing the division; and transmitting means for transmitting thedetermination flag of each block along with each coded hierarchy data.Therefore, the division decision flag for deciding the way of divisionof block can be confirmed.

Further, in the present invention, a picture coding apparatus for codinginputted picture signal, to sequentially and recursively generate pluralhierarchy data each having a different resolution, comprises:determination controlling means for detecting the block activity valueof all of the blocks of respective hierarchy data excepting theuppermost hierarchy data having the lowest resolution, for generatingthe division determination flag for determining the division of the eachblock based on the block activity value, and when the determined resultshowing that the block activity value is smaller than the predeterminedthreshold value is obtained, for generating the division stop flag forstopping the division of the block, and when the determined resultshowing that the block activity value is greater than or equal to thepredetermined threshold value is obtained, for generating the divisioncontinue flag for continuing the division of the block; and transmittingmeans for transmitting the determination flag of each block along witheach coded hierarchy data. Therefore, the way of division of block canbe decided independently.

Further, in the present invention, a picture coding apparatus for codinginputted picture signal being a plurality of picture forming signals,which have a correlation each other to form a picture, in order tosequentially and recursively generate plural hierarchy data each havinga different resolution, comprises determination controlling means fordetecting the block activity value which corresponds to the first signalout of a plurality of picture forming signals as to a predeterminedblock of each hierarchy data excepting the uppermost hierarchy datahaving the lowest resolution, for generating the division determinationflag for determining the division of the block or the division of alower block which corresponds to the block, and when the determinedresult showing that the block activity value is smaller than thepredetermined threshold value is obtained, for generating the divisionstop flag for stopping the division of the block or the division of thelower block which corresponds to the block, and when the determinedresult showing that the block activity value is greater than or equal tothe predetermined threshold value is obtained, for generating thedivision continue flag for continuing the division of the block or thedivision of the lower block which corresponds to the block, and then fordetermining the threshold value on the basis of the second signal out ofthe plurality of picture forming signals. Therefore, the threshold valueis set by the first signal such as the luminance signal, and thedivision of the second signal such as the color signal can be performed.

Further, in the present invention, a picture coding apparatus for codinginputted picture signal which is utilized to sequentially andrecursively generate plural hierarchy data each having a differentresolution, comprises: threshold value detecting means for detecting athreshold value being a standard of determination of block activitybased on the block activity value of all of the blocks of each hierarchydata, to control generated information quantity so as to attain to thetarget value; determining and dividing means for detecting the blockactivity of a predetermined block of each hierarchy data excepting theuppermost hierarchy data having the lowest resolution, and fordetermining the way of division of the block or division of a lowerblock which corresponds to the block based on the comparison result ofthe block activity and the threshold value and performing the division;and transmitting means for transmitting the hierarchical coded datawhich is obtained from the determining and dividing means. Therefore,when the block activity value become less than the predetermined value,(that is when the change of picture become small), the generatedinformation quantity by division processing of the lower hierarchy iscontrolled.

Furthermore, in the present invention, a picture coding apparatus forcoding inputted picture signal, to recursively generate plural hierarchydata each having a different resolution, comprises: determining anddividing means for determining the way of adaptive division of a blockwhich corresponds to the characteristic of the picture data, and fordividing the picture data on the basis of the determined result; andtransmitting means for transmitting variable-length data aftertransmitted the hierarchical coded data obtained from the determiningmeans as fixed-length data. Thereby, transmitting efficiency of data canbe improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a picture coding apparatus using aconventional pyramidal coding method;

FIG. 2 is a block diagram showing a picture decoding apparatus whichcorresponds to the picture coding apparatus of FIG. 1;

FIG. 3 is a schematic diagram explaining the principle of thehierarchical encoding according to the present invention;

FIG. 4 is a table showing a result of an adaptive division of the HDstandard picture obtained by the use of the hierarchical codingprinciple of FIG. 3;

FIG. 5 is a table showing a standard deviation of the signal level, ofeach hierarchy, of the HD standard picture obtained by the use of thehierarchical coding principle of FIG. 3;

FIG. 6 is a block diagram showing the picture coding apparatus of thefirst embodiment according to the present invention;

FIG. 7 is a schematic diagram illustrating a construction of hierarchydata in hierarchical coding;

FIG. 8 is a block diagram showing the picture decoding apparatus of thefirst embodiment;

FIG. 9 is a block diagram showing another embodiment of the firstembodiment;

FIG. 10 is a block diagram showing the picture encoding apparatus of thesecond embodiment according to the present invention;

FIG. 11 is a block diagram showing the picture coding apparatus of thethird embodiment according to the present invention;

FIG. 12 is a block diagram showing the hierarchical coding encoder unitof FIG. 11;

FIG. 13 is a block diagram showing the decoder of FIG. 12;

FIG. 14 is a block diagram showing the coder of FIG. 12;

FIGS. 15(A) to 15(E) are schematic diagrams explaining a hierarchicalstructure;

FIG. 16 is a block diagram showing a generated information quantitycontrol unit;

FIGS. 17(A) to 17(E) are characteristic curvilinear diagramsillustrating the frequency table of each hierarchy;

FIG. 18 is a table showing a combination of threshold values obtainedfor each hierarchy;

FIG. 19 is a characteristic curvilinear diagram illustrating a frequencytable;

FIG. 20 is a characteristic curvilinear diagram illustrating anintegrating frequency table;

FIG. 21 is a characteristic curvilinear diagram illustrating a frequencytable;

FIG. 22 is a characteristic curvilinear diagram illustrating anintegrating frequency table;

FIG. 23 is a block diagram showing the picture coding apparatus of thefourth embodiment according to the present invention;

FIG. 24 is a block diagram showing the hierarchical coding encoder unitof FIG. 23;

FIG. 25 is a block diagram showing the coder of FIG. 24;

FIG. 26 is a block diagram showing a generated information quantitycontrol unit;

FIGS. 27(A) to 27(E) are characteristic curvilinear diagramsillustrating the frequency table of each hierarchy;

FIGS. 28(A), 28(B), 29, 30(A), 30(B), and 31 are characteristiccurvilinear diagrams illustrating an example of the frequency table;

FIG. 32 is a characteristic curvilinear diagram illustrating anintegrating frequency table;

FIG. 33 is a characteristic curvilinear diagram illustrating thefrequency table which uses a clipped value;

FIG. 34 is a characteristic curvilinear diagram illustrating theintegrating frequency table which uses the clipped value;

FIG. 35 is a flowchart showing a processing procedure of thehierarchical coding;

FIG. 36 is a block diagram showing the picture coding apparatus of thefifth embodiment according to the present invention;

FIG. 37 is a block diagram showing the hierarchical coding encoder unitof FIG. 36;

FIG. 38 is a block diagram showing the coder of FIG. 37;

FIG. 39 is a block diagram showing a generated information quantitycontrol unit;

FIGS. 40(A) to 40(E) are characteristic curvilinear diagramsillustrating the frequency table of each hierarchy;

FIGS. 41(A), 41(B), 42, 43(A), 43(B), and 44 are characteristiccurvilinear diagrams illustrating an example of the frequency table;

FIG. 45 is a characteristic curvilinear diagram illustrating anintegrating frequency table;

FIG. 46 is a characteristic curvilinear diagram illustrating thefrequency table which uses the clipped value;

FIG. 47 is a characteristic curvilinear diagram illustrating theintegrating frequency table which uses the clipped value;

FIG. 48 is a flowchart showing a processing of the hierarchical coding;

FIG. 49 is a block diagram showing the picture coding apparatus of thesixth embodiment according to the present invention;

FIG. 50 is a block diagram showing the hierarchical coding encoder unitof FIG. 49;

FIG. 51 is a block diagram showing the coder of FIG. 50;

FIGS. 52(A) to 52(E) are schematic diagrams explaining a hierarchicalstructure;

FIG. 53 is a signal waveform diagram illustrating the divided result ofa color signal;

FIG. 54 is a flowchart showing a processing of the hierarchical coding;

FIG. 55 is a block diagram showing the picture coding apparatus of theseventh embodiment according to the present invention; and

FIG. 56 is a conceptional plane view illustrating the data structure oftransmitting block.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described in detail withreference to the drawings.

1! Principle of the Hierarchical Coding

FIG. 3 generally shows the case where, for example, a static picture ofthe high definition television signal and the like is hierarchicallycoded and compressed, as the principle of the hierarchical codingaccording to the present invention. In this hierarchical coding, theupper hierarchy data is produced by a simple arithmetic mean of thelower hierarchy data in order to reduce the lower hierarchy data to betransmitted, hereby a hierarchical structure is realized which does notaccompany any increasing of the information quantity. As to decodingfrom the upper hierarchy data to the lower hierarchy data, division isadaptively controlled based on the activity value of each block, so thatthe information quantity of a plane portion is reduced.

Here, the block activity is a correlation value which is represented bya maximum value, a mean value, a sum of absolute values, a standarddeviation, or an n-th power sum, of the inter-hierarchy difference dataD41 to D44 in the specific block in the case where the lower hierarchydata area corresponding to the upper hierarchy data is defined as"block". That is, when the activity value is lower, it may safely besaid that this block is a plane block.

Further, in the coding of inter-hierarchy difference data which isperformed for the sake of the lower hierarchy data, an increase of theefficiency is realized by switching the quantization characteristics foreach block without any additional code based on the activity value ofthe upper hierarchy data.

That is, in the hierarchical structure of this hierarchical coding, aninputted high definition television signal is selected as the lowermosthierarchy data first, and the arithmetic mean of the four pixels X₁ toX₄ in the small block of 2 lines×2 pixels of this lowermost hierarchydata is obtained by the following equation:

    m=(X.sub.1 +X.sub.2 +X.sub.3 +X.sub.4)/4                   (1)

and the value "m" is set to the value of the upper hierarchy data. Inthis lower hierarchy data, as shown in the following equation:

    ΔX.sub.i =X.sub.i -m (where i=1 to 3)                (2)

the inter-hierarchy difference data to the upper hierarchy data isprepared for only three pixels, so that the hierarchical structure isformed with the same information quantity as the original four-pixeldata.

Meanwhile, in decoding of the lower hierarchy data, as to three pixelsX₁ to X₃, the mean value "m" of the upper hierarchy data is added to therespective inter-hierarchy difference data ΔX_(i) as shown in thefollowing equation:

    E X.sub.i !=ΔX.sub.i +m (where i=1 to 3)             (3)

hereby the decoded values E X_(i) ! is given. Then, the three decodedvalues of the lower hierarchy data are subtracted from the mean value"m" of the upper hierarchy data as shown in the following equation:

    E X.sub.4 !=m×4-E X.sub.1 !-E X.sub.2 !-E X.sub.3 !  (4)

hereby the decoded value E X₄ ! of the remaining one pixel isdetermined. Where E ! denotes a decoded value.

Here, in this hierarchical coding, the resolution and the data quantityare quadruplicated per hierarchy from an upper hierarchy to a lowerhierarchy, however, this division is inhibited on a plane portion sothat the redundancy is decreased. A single bit flag for indicatingwhether this division is there or not is prepared for each block. Thenecessity of division at the lower hierarchy is determined based on themaximum value of the inter-hierarchy difference data and so on, as alocal activity value.

As an example of this hierarchical coding, FIG. 4 shows a result of anadaptive division in which the HD standard picture (Y signal) of the ITEis utilized and divided into five-hierarchy and coded. It shows a ratioof a number of pixels of each hierarchy when a threshold value withrespect to the maximum inter-hierarchy difference data is changed, to anumber of original pixels, hereby a circumstances of redundancydecreasing based on a spatial correlation can be seen. A decreasingefficiency changes depends on pictures. When the threshold value withrespect to the maximum inter-hierarchy difference data is changed from 1to 6, the mean decreasing rate becomes 28 to 69 %!.

In practice, the resolution of the upper hierarchy data is quadrupled soas to produce the lower hierarchy data, hence the inter-hierarchydifference data from the upper hierarchy data is coded, so that thesignal level width can be effectively decreased in the lower hierarchydata. FIG. 5 shows a case of five hierarchies which are given by thehierarchical coding mentioned above with respect to FIG. 4, wherein thehierarchies are defined as the first to the fifth hierarchies in theorder which begins from the lowest one. It is seen that the signal levelwidth is reduced in comparison with the 8 bit PCM data of the originalpicture. Because the first to the fourth hierarchies which have manypixels are inter-hierarchy difference data, a substantial reduction canbe attained, therefore the efficiency is improved in the subsequentquantization. As may be seen from FIG. 5, its reduction efficiency showslittle dependency to patterns, and it is effective to all pictures.

Further, because the upper hierarchy data is produced from a mean valueof the lower hierarchy data, error propagation can be restricted withinits block, while the lower hierarchy data is transformed to thedifferences from the mean value of the upper hierarchy data, thereby anexcellent efficiency can also be obtained. In practice, on ahierarchical coding, there is correlation in the activities of the samespatial positions among the hierarchies. A quantization characteristicsof the lower hierarchy data is determined from the result ofquantization of the upper hierarchy data, hereby an adaptive quantizercan be realized which does not require to transmit quantizationinformation used at the sending side (encoding side) to the receivingside (decoding side) (excepting the initial value).

In practice, a picture is hierarchically coded based on theabovementioned 5-stage hierarchical structure and is represented bymulti-resolution, and an adaptive division and an adaptive quantizationwhich utilizes a hierarchical structure are performed, so that variouskinds of HD standard pictures (Y/P_(B) /P_(R) of 8 bits) can becompressed into about 1/8. Further, an additive code for each blockwhich is prepared for adaptive division, is subjected to a run-lengthcoding at each hierarchy to improve the compression efficiency. In thismanner, a picture having sufficient picture quality can be obtained ateach hierarchy, and the final lowermost hierarchy can also obtains asatisfactory picture without a visual degradation.

2! First Embodiment

(1) Picture Coding Apparatus of the First Embodiment

Referring to FIG. 6, reference numeral 140 generally shows a picturecoding apparatus according to the present invention, in which an inputpicture data D131 being a static picture, for example, of thehigh-definition television signal etc. is divided into five hierarchiesby means of the abovedescribed hierarchical coding method, and thusobtained lowermost hierarchy data and inter-hierarchy difference datafor four hierarchies are coded. In practice, in the picture codingapparatus 140, the input picture data D131 is inputted to the firstdifference circuit 141 and the first averaging circuit 142.

As shown in FIG. 7, the first averaging circuit 142 generates a pixelX1(2) of the second hierarchy data D132 from the four pixels X1(1)-X4(1)of the input picture data D131 which is composed of the first hierarchydata being the lowermost hierarchy. In the same manner, pixelsX2(2)-X4(2) adjacent to the pixel X1(2) of the second hierarchy dataD132 are generated by the average of the four pixels of the firsthierarchy data D131. The second hierarchy data D132 is inputted to thesecond difference circuit 143 and the second averaging circuit 144. Thesecond averaging circuit 144 generates a pixel X1(3) of the thirdhierarchy data D133 by the average of the four pixels of the pixelsX1(2)-X4(2) of the second hierarchy data D132. Similarly, pixelsX2(3)-X4(3) adjacent to the pixel X1(3) of the third hierarchy data D133are generated by the average of the four pixels of the second hierarchydata D132.

Further, the third hierarchy data D133 is inputted to the thirddifference circuit 145 and the third averaging circuit 146. The thirdaveraging circuit 146 generates pixels X1(4)-X4(4) of the fourthhierarchy data D134 by the average of the four pixels X1(3)-X4(3) of thethird hierarchy data D133 in the same manner as the above. This fourthhierarchy data D134 is inputted to the fourth difference circuit 147 andthe fourth averaging circuit 148. The fourth averaging circuit 148generates the fifth hierarchy data D135 which is the uppermost hierarchyby the average of the four pixels X1(4)-X4(4) of the fourth hierarchydata D134 similarly to the above.

In practice, regarding the block sizes of the first to the fifthhierarchy data D131 to D135, when the block size of the first hierarchydata D131 being the lowermost hierarchy is 1×1, the second hierarchydata D132 is 1/2×1/2, the third hierarchy data D133 is 1/4×1/4, thefourth hierarchy data D134 is 1/8×1/8, and the fifth hierarchy data D135being the uppermost hierarchy data is 1/16×1/16.

In this manner, the first to the fourth hierarchy data, which are otherthan the fifth hierarchy data D135 of the uppermost hierarchy among fivehierarchy data D131 to D135, are difference-calculated each other, atthe first, the second, the third, and the forth difference circuits 141,143, 145, and 147 as described above accompanying with Equation (2), togenerate inter-hierarchy difference data D140, D141, D142, and D143.

In practice, first, the fifth hierarchy data D135 and the fourthhierarchy data D134 are calculated the difference at the fourthdifference circuit 147 to generate the inter-hierarchy difference dataD143 of the fourth hierarchy. Secondly, the fourth hierarchy data D134and the third hierarchy data D133 are calculated the difference at thethird difference circuit 145 to generate the inter-hierarchy differencedata D142 of the third hierarchy. Thirdly, the third hierarchy data D133and the second hierarchy data D132 are calculated the difference at thesecond difference circuit 143 to generate the inter-hierarchy differencedata D141 of the second hierarchy. Lastly, the second hierarchy dataD132 and the first hierarchy data D131 are calculated the difference atthe first difference circuit 141 to generate the inter-hierarchydifference data D140 of the first hierarchy.

As the above, in the picture coding apparatus 140 of this embodiment,the fifth hierarchy data D135 and the inter-hierarchy difference dataD143 to D140 of the fourth to the first hierarchies are sequentiallygenerated in this order. At this time, in the picture coding apparatus140, the lower hierarchy data is generated in association with the upperhierarchy data so that one pixel is reduced from four pixels of thelower hierarchy corresponding to the one pixel of the upper hierarchy bycoders 154 to 157, thereby, the lowering of the compression efficiencycan be avoided even if a picture data is divided into a plurality ofhierarchies and coded.

These inter-hierarchy difference data D140 to D143 are inputtedrespectively to division control circuits 150, 151, 152, and 153. Thisdivision control circuits 150 to 153 perform the determination betweenthe threshold value Tha and the block activity which represents whetheror not the specified block in the inter-hierarchy difference data D140to D143 is a plane portion, every time in the order from theinter-hierarchy difference data D143 to D140 of the upper hierarchy, anddetermine whether or not to transmit the following inter-hierarchydifference data D142 to D140. For example, assuming that the activityvalue in the block of the inter-hierarchy difference data D143 of thefourth hierarchy is "A", when satisfying the following equation:

    A<Tha                                                      (5)

the picture data is determined as a plane portion and a block in whichthe deterioration is hardly occurred, and then the determination flag Frepresenting no transmission is set. In this manner, the divisioncontrol circuits 150 to 153 perform the determination between thethreshold value Tha and the block activity every time, with respect toall of the blocks of the inter-hierarchy difference data D140 to D143 ofeach hierarchy, and as a result, the determination flag F representingwhether or not to transmit the corresponding block is outputted to acontrol code generating circuit 159.

At the same time, the division control circuit 153 outputs the controlsignal C3 to the division control circuit 152 of the third hierarchy. Asa result, the division control circuit 152 of the third hierarchy stopsunconditionally the transmission of the inter-hierarchy difference dataD142. The division control circuit 152 of the third hierarchy and thedivision control circuit 153 of the second hierarchy receive the controlsignals C3 and C2 which represent unconditioned stop of transmission,and output this as it is to the lower division control circuits 151, 150as the control signals C2, C1 respectively. Thereby, transmission of theinter-hierarchy difference data D142 to D140 of all of the lowerhierarchies are stopped unconditionally by the control of the divisioncontrol circuits 153 to 150.

In this manner, the inter-hierarchy difference data D140 to D143 of eachhierarchy which are outputted from the division control circuits 150 to153, are outputted to the coders 154 to 157. On the other hand, thefifth hierarchy data D135 of the uppermost hierarchy is outputted to thecoder 158 as it is. The coders 154 to 157 compress and code theinter-hierarchy difference data D140 to D143 by means of the non-linearcoding method which applies to the coding of difference data, so thatthe first to the fourth hierarchy compression-coded data D145 to D148are generated. On the other hand, the coder 158 compression-codes thefifth hierarchy data D135 by means of the linear coding method whichapplies to the coding of picture data being mean value data, so that thefifth hierarchy compression-coded data D149 is generated.

The determination flag F outputted from the respective division controlcircuits 150 to 153 is inputted to the control code generating circuit159. Then, the control code generating circuit 159 generates the controlcode D150 which is composed of the determination flags F of eachhierarchy and each block. The control code D150 and the first to thefifth hierarchy compression-coded data D145 to D149 are, after coded bymeans of the run-length coding and so on, divided into frames bypredetermined transmission data forming unit (not shown), and then theseare transmitted to the transmission lines.

Thus transmitted the first to the fifth hierarchy compression-coded dataD145 to D149 and the control code D150 are decoded by the picturedecoding apparatus 160 shown in FIG. 8. More specifically, the first tothe fifth hierarchy compression-coded data D145 to D149 are inputted tothe decoders 161 to 165 which have the decoding technique inverse to thecoding of the coders 154 to 158. As a result, the inter-hierarchydifference data D151 to D154 of the first to the fourth hierarchieswhich are decoded by the decoders 161 to 164, are inputted respectivelyvia the division control circuits 170 to 173 of the first to the fourthhierarchies to the first to the fourth adding circuits 175 to 178.

On the other hand, the fifth hierarchy compression-coded data D149 isdecoded at the decoder 165. Thus obtained fifth hierarchy data D155 isoutputted as it is to the fourth adding circuit 178. The fourth addingcircuit 178 adds the fifth hierarchy data D155 and the inter-hierarchydifference data D154 of the four th hierarchy to restore the fourthhierarchy data D159, and outputs it to the third adding circuit 177.

Similarly, the third adding circuit 177 adds the restored fourthhierarchy data D159 and the inter-hierarchy difference data D153 of thethird hierarchy to restore the third hierarchy data D158, and outputs itto the second adding circuit 176. In the same manner, the secondhierarchy data D157 and the first hierarchy data D156 are restored fromthe second adding circuit 176 and the first adding circuit 175, andsimilarly, the first to the fourth, and the fifth hierarchy data D156 toD159, and D155 are outputted.

The control code D150 is inputted to the control code analyzing circuit166. The control code analyzing circuit 166 analyzes that if thetransmission stop of the inter-hierarchy difference data has occurred,based on the inputted control code D150, and outputs the analysis resultto the division control circuits 170 to 173 as the transmission stopflag F. If it is detected that the transmission stop of theinter-hierarchy difference data has occurred, based on the inputtedtransmission stop flag F, the division control circuits 170 to 173generate the inter-hierarchy difference data of the value "0", forexample as a dummy data, instead of the inter-hierarchy difference data,and output it to the adding circuits 175 to 178.

As the above, in the picture coding apparatus 140, only control datarepresenting transmission stop is transmitted in accordance with theblock activity of the inter-hierarchy difference data, withouttransmitting the inter-hierarchy difference data of unnecessary block,so that the hierarchy data can be certainly restored based on thecontrol data in the picture decoding apparatus 160.

According to the above construction, the block activity of the specifiedblock of the inter-hierarchy difference data of each hierarchy exceptingthe uppermost hierarchy is determined, and when the block activity isless than the specified threshold value, the division stop flag is setas the determination flag of a plurality of lower blocks correspondingto the block in the inter-hierarchy difference data of adjacent lowerhierarchies, and at the same time, determination of the block activityof the plurality of lower blocks and transmission of the plurality oflower blocks are stopped, and then the determination flag for each blockis transmitted along with the coded code, so that the coded data inunnecessary block can not be transmitted in accordance with the blockactivity of the inter-hierarchy difference data. Thereby, a picturecoding method and a picture coding apparatus in which the quantity ofcodes can be reduced and the compression efficiency of the coded datacan be improved, can be realized.

(2) Other Embodiments of First Embodiment

(2-1) In the embodiment described above, such a case is described thatthe transmission is stopped by which, the block activity value isdetermined in the block of the inter-hierarchy difference, and when theblock activity is less than the specified threshold value, the controlsignals C1, C2, and C3 which designate the division stop for the lowerhierarchy, and at the same time, the division stop flag is set as thedetermination flag of the plurality of lower blocks which correspond tothe block in the lower inter-hierarchy difference data. However, thepresent invention is not only limited to this, but as shown in FIG. 9,when the block activity value is less than the specified thresholdvalue, the control signals C1, C2, and C3 which designate the divisionstop is output for the lower hierarchy, and the division stop flag istemporarily set as the determination flag of the plurality of lowerblocks which correspond to the block in the lower inter-hierarchydifference data; when the block activity of any one of the plurality ofblocks is the specified threshold value or more, the control signals C4,C5, and C6 which divide again are outputted to the division controlcircuits 151, 152, or 153 of the upper hierarchy, and the division stopflag can be changed to the division continue flag and then thedetermination flag for each block can be transmitted along with thecoded code.

In this connection, to accomplish this, in the picture coding apparatusdescribed above accompanying with FIG. 6, determination of the blockactivity value is performed with respect to all of the inter-hierarchydifference data at the division control circuit. If it is detected thatthe block activity value is the threshold value or more, it is neededthat the designation for changing the transmission stop command totransmission continue command is outputted from the lower divisioncontrol circuit to the upper division control circuit, even if thecontrol data of transmission stop is inputted from the upper divisioncontrol circuit.

(2-2) In the embodiments described above, such a case is described thata picture data is sequentially and recursively divided into pluralhierarchy data having a plurality of resolutions different from eachother, and the uppermost hierarchy data having the lowest resolution andinter-hierarchy difference data for a plurality of hierarchies which iscomposed of the difference value between respective hierarchy dataexcepting the uppermost hierarchy data and the adjacent upper hierarchydata, are coded. However, the present invention is not only limited tothis, but may be applied to the case where a picture data issequentially and recursively divided into plural hierarchy data having aplurality of resolutions different from each other and coded. In thiscase, the same effects as the embodiments described above can berealized by determination of the block activity value is also performedwith respect to the block of the hierarchy data instead of theinter-hierarchy difference data.

(2-3) Further, in the embodiments described above, such a case isdescribed that the determination between the maximum value and thethreshold value in the block is performed as the block activity.However, the present invention is not only limited to this, but thedetermination between the threshold, and a mean value, a sum of absolutevalues, a standard deviation, an n-th power sum, can be performed as theblock activity. Further, the same effects as the embodiments describedabove can be realized by using the data frequency over the specifiedthreshold value in the block.

(2-4) Further, in the embodiments described above, such a case isdescribed that when a picture data is divided into plural hierarchydata, the adjacent upper hierarchy data is sequentially and recursivelyformed by averaging the calculation result for each specified block ofthe picture data or adjacent lower hierarchy data. However, the presentinvention is not only limited to this, but adjacent upper hierarchy datacan be recursively formed by averaging the weighting such as taking theaverage by prescribed weighting. Further, the present invention is alsoapplicable to the case where the upper hierarchy data is recursivelyformed by means of the other method such as the decimating.

(2-5) Further, in the embodiments described above, such a case isdescribed that the block activity value in the block is determined tostop the transmission of the lower hierarchy data. However, whether ornot to stop the transmission is not only limited to use the blockactivity value, but can use the other characteristic of the picturedata. In this manner, by the division of the adaptive block is performedcorresponding to the characteristic of the picture data, the codingefficiency can be improved.

(3) As described above, according to the present invention, when apicture data represented by using a recursive hierarchicalrepresentation is hierarchically coded, the picture data is divided intothe blocks adaptively corresponding to the characteristic of the picturedata and is coded, and the hierarchical coded data obtained as a resultof the division is transmitted in order to perform the division of thelower blocks adaptively. Thereby, a picture coding method and a picturecoding apparatus in which the information quantity of plane portion of apicture can be reduced, can be realized.

The block activity value of the specified block of the hierarchy dataexcepting the uppermost hierarchy data having the lowest resolution isdetermined, and when the block activity value is less than the specifiedthreshold value, a division stop flag is set as a determination flag ofa plurality of lower blocks corresponding to the block in the adjacentlower hierarchy data, and at this time, the determination of the blockactivity value of the plurality of lower blocks and transmission of theplurality of lower blocks are stopped and the determination flag foreach block is transmitted along with the coded code, so as not totransmit the coded data of unnecessary block in accordance with theblock activity value of the hierarchy data. Thereby, the picture codingmethod and the picture coding apparatus in which the quantity of codescan be reduced and the compression efficiency of the coded data can beimproved, can be realized.

Further, the block activity of the specified block of theinter-hierarchy difference data of the respective hierarchies exceptingthe uppermost hierarchy is determined, and when the block activity isless than the specified threshold value, a division stop flag is set asa determination flag of a plurality of lower blocks corresponding to theblock in the inter-hierarchy difference data of adjacent lower hierarchydata, and at this time, the determination of the block activity value ofthe plurality of lower blocks and transmission of the plurality of lowerblocks are stopped and the determination flag for each block istransmitted along with the coded code, so as not to transmit the codeddata of unnecessary block in accordance with the block activity value ofthe inter-hierarchy difference data. Thereby, the picture coding methodand the picture coding apparatus in which the quantity of codes can bereduced and the compression efficiency of coded data can be improved,can be realized.

Further, the block activity value of the specified block in thehierarchy data excepting the uppermost hierarchy data having the lowestresolution is determined, and when the block activity value is less thanthe specified threshold value, a division stop flag is temporarily setas a determination flag of the plurality of lower blocks correspondingto the block in adjacent lower hierarchy data. When the block activityvalue of any one of the plurality of lower blocks is the specified valueor more, the division stop flag is changed to division continue flag andthe determination flag for each block is transmitted along with thecoded code, so as not to transmit unnecessary coded data by determiningthe necessity of the block in accordance with the block activity of thehierarchy data with avoiding the deterioration of the picture qualitypreviously. Thereby, the picture coding method and the picture codingapparatus in which the quantity of codes can be reduced and thecompression efficiency of the coded data can be improved, can berealized.

Further, the block activity value of the specified block of theinter-hierarchy difference data of the respective hierarchies exceptingthe uppermost hierarchy are determined, and when the block activityvalue is less than the specified threshold value, the division stop flagis temporarily set as a determination flag of the plurality of lowerblocks corresponding to the block in the adjacent lower hierarchy data.When the block activity value of any plurality of lower blocks is thespecified threshold value or more, the division stop flag is changed todivision continue flag and the determination flag for each block istransmitted along with the coded code, so as to determine the necessityof the block in accordance with the block activity of theinter-hierarchy difference data with avoiding the deterioration ofpicture quality previously and not to transmit unnecessary coded data.Thereby, the picture coding method and the picture coding apparatus inwhich the quantity of codes can be reduced and the compressionefficiency of the coded data can be improved, can be realized.

3! Second Embodiment

(1) Picture Coding Apparatus of the Second Embodiment

FIG. 10 shows the second embodiment in which the corresponding part toFIG. 6 is attached the same numeral. In this case, the division controlcircuits 150 to 153 of the picture coding apparatus 190 perform adetermination between the threshold value Tha and the block activitywhich represents if the predetermined block in the inter-hierarchydifference data D140 to D143 is a plane portion, every time for therespective block of the inter-hierarchy difference data D140 to D143 ofeach hierarchy, to determine the processing whether or not to transmitthe corresponding block of the above inter-hierarchy difference dataD140 to D143.

For example, assuming the activity in the block of the inter-hierarchydifference data D143 of the fourth hierarchy as "A", when satisfying thefollowing equation:

    A<Tha                                                      (6)

the picture data is determined as a plane portion and a block in whichthe deterioration is hardly occurred. Then the determination flag Frepresenting that the block is not transmitted is set. In this manner,the division control circuits 150 to 153 perform the determinationbetween the threshold value Tha and the block activity every time, withrespect to all of the blocks of the inter-hierarchy difference data D140to D143 of each hierarchy, and output the determination flag Frepresenting that whether or not to transmit the corresponding block, tothe control code generating circuit 159.

The inter-hierarchy difference data D140 to D143 of each hierarchy whichare outputted from the division control circuits 150 to 153 in thismanner, are also outputted to the coders 154, 155, 156, and 157. Thefifth hierarchy data D135 of the uppermost hierarchy is outputted to thecoder 158 as it is. The coders 154, 155, 156, and 157 compression-codethe inter-hierarchy difference data D140 to D143 by means of thenon-linear coding method which applies to the coding of difference data,so that the first to the fourth hierarchy compression-coded data D145 toD148 are generated. Further, the coder 158 compression-codes the fifthhierarchy data D135 by means of the non-linear coding method whichapplies to the coding of the picture data being mean value data, so thatthe fifth hierarchy compression-coded data D149 is generated. The firstto the fifth hierarchy compression-coded data D145 to D149 and thecontrol codes are divided into frames by a predetermined transmissiondata forming unit (not shown) and outputted to the transmission line.

In this manner, by determining the block activity of the inter-hierarchydifference data in the picture coding apparatus 190, only control datarepresenting the transmission stop is transmitted without transmittingunnecessary block, so that the hierarchy data can be certainly restoredbased on the control data by the picture decoding apparatus 160 (FIG.8).

According to the above construction, the block activity is determinedevery time as to all of the blocks of the inter-hierarchy differencedata of each hierarchy excepting the uppermost hierarchy, and theprocessing of the inter-hierarchy difference data in the block isselected based on the determined result, so that the generatedinformation quantity in the block can be reduced by controllingseparately. Thereby, the compression efficiency when the picture data ishierarchically coded, can be improved.

(2) Other Embodiments of Second Embodiment

(2-1) In the embodiment described above, such a case is described that apicture data is sequentially and recursively divided into pluralhierarchy data having a plurality of resolutions different from eachother, and the uppermost hierarchy data having the lowest resolution,and the inter-hierarchy difference data for a plurality of hierarchieswhich is composed of the difference value between the respectivehierarchy data excepting the uppermost hierarchy data and the adjacentupper hierarchy data, are coded. However, the present invention is notonly limited to this, but can be applied to the case where a picturedata is sequentially and recursively divided into plural hierarchy datahaving a plurality of resolutions different from each other and coded.In this case, the same effects as the embodiments described above can berealized by the determination of the block activity is also performedwith respect to the block of the hierarchy data, instead of theinter-hierarchy difference data.

(2-2) In the embodiments described above, such a case is described thatthe determination between the maximum value and the threshold value in ablock is performed as the block activity. However, the present inventionis not only limited to this, but the determination between a thresholdvalue, and a mean value, a sum of absolute values, a standard deviation,an n-th power sum can be performed as the block activity. Further, thesame effects as the embodiments described above can be realized even ifthe data frequency over the specified threshold value in the block isused.

(2-3) In the embodiments described above, such a case is described thatwhen a picture data is divided into plural hierarchy data, adjacentupper hierarchy data is sequentially and recursively formed by averagingthe calculation result for each specified block of the picture data orthe adjacent lower hierarchy data. However, the present invention is notonly limited to this, but the adjacent upper hierarchy data can berecursively formed by averaging the weighting such as taking the averageby prescribed weighting. Further, the present invention is alsoapplicable to the case where the upper hierarchy data is recursivelyformed by means of the decimating or the like.

(3) As described above, according to the present invention, the blockactivity value is determined every time as to all of the blocks of thehierarchy data excepting the uppermost hierarchy data having the lowestresolution, and the processing of the hierarchy data in the block isselected based on the determined result, so that the generatedinformation quantity in the block can be reduced by separatelycontrolling. Thereby, the picture coding method and the picture codingapparatus in which the compression efficiency when the picture data ishierarchically coded, can be realized.

The block activity value is determined every time as to all of theblocks of the inter-hierarchy difference data of the respectivehierarchies excepting the uppermost hierarchy, and the processing of theinter-hierarchy difference data in the block is selected in accordancewith the above determined result, so that the generated informationquantity in the block can be reduced by separately controlling. Thereby,the picture coding method and the picture coding apparatus in which thecompression efficiency when the picture data is hierarchically coded canbe improved, can be realized.

4! Third Embodiment

(1) Picture Coding Apparatus of the Third Embodiment

FIG. 11 shows the picture coding apparatus 40 of the third embodiment,which is compose d of a hierarchical coding encoder unit 40A forhierarchically coding an input picture data D31 and outputting it, and agenerated information quantity control unit 40B for controlling thegenerated information quantity in the hierarchical coding encoder unit40A so as to attain the target value.

The hierarchical coding encoder unit 40A is composed of a data delayingmemory (not shown) and an encoder. The memory is provided in theinputting stage in order that the data can be delayed, so that theencoding processing will not be performed until an optimal control valueis determined in the generated information quantity control unit 40B.

Meanwhile, the generated information quantity control unit 40B inputs aninput picture data and then determines a threshold value TH which isaccommodated to the data to be processed, and also transmits the optimalcontrol value, which is determined so that the inputted picture datawill be efficiently coded in the hierarchical coding encoder unit 40A,to the encoder. It has a construction of a so-called feed-forward typebuffering. By virtue of this construction, the generated informationquantity can be controlled separately, and a time delay generated by thefeed-forward type buffering can be eliminated.

(2) Hierarchical Coding Encoder Unit 40A

(2-1) Structure of Block

The hierarchical coding encoder unit 40A has the construction shown inFIG. 12, and in the case of this example, processes by dividing intofive hierarshies.

At first, an input picture data D31 is inputted to the first differencecircuit 41 and the first averaging circuit 42. The first averagingcircuit 42 generates the second hierarchy data D32, by averaging thefour pixels of the input picture data D31 (that is, the first hierarchydata (the lowest hierarchy data)). In the case of this embodiment, thefirst averaging circuit 42 generates a pixel X1(2) of the secondhierarchy data D2, from the four pixels X1(1)-X4(1) of the input picturedata D31, as shown in FIGS. 15(D) and 15(E).

In the same manner, the pixels X2(2)-X4(2), which are adjacent to thepixel X1(2) of the second hierarchy data D32, are generated by averagingthe four pixels of the first hierarchy data D31.

The second hierarchy data D32 is inputted to the second differencecircuit 43 and the second averaging circuit 44. The second averagingcircuit 44 generates the third hierarchy data D33, by averaging the fourpixels of the second hierarchy data D32. For instance, the pixel X1(3)of the third hierarchy data D33 which is shown in FIG. 15(C) isgenerated by the pixels X1(2)-X4(2) of the second hierarchy data D32which is shown in FIG. 15(D). The pixels X2(3)-X4(3) which are adjacentto the pixel X1(3) are similarly generated by averaging the four pixelsof the second hierarchy data D32.

The third hierarchy data D33 is inputted to the third difference circuit45 and the third averaging circuit 46. As shown in FIGS. 15(B) and15(C), the third averaging circuit 46 generates the fourth hierarchydata D34 which is composed of the pixels X1(4)-X4(4), by averaging thefour pixels of the third hierarchy data D33 in the same manner as theforegoing.

The fourth hierarchy data D34 is inputted to the fourth differencecircuit 47 and the fourth averaging circuit 48. The fourth averagingcircuit 48 generates the fifth hierarchy data D35 which is the uppermosthierarchy, by averaging the four pixels of the fourth hierarchy dataD34. That is to say, the pixel X1(5) of the fifth hierarchy data D35 isgenerated by averaging the four pixels X1(4)-X4(4) of the fourthhierarchy data D34, as shown in FIGS. 15(A) and 15(B).

With regard to the block sizes of the first to the fifth hierarchy dataD31 to D35, assuming that the block size of the data D31 of the firsthierarchy which is the lowest hierarchy, is 1 line×1 pixel, then theblock size of the second hierarchy data D32 appears as 1/2 line×1/2pixel, the block size of the third hierarchy data D33 appears as 1/2line×1/4 pixel, the block size of the fourth hierarchy data D34 appearsas 1/8 line×1/8 pixel, and the block size of the fifth hierarchy dataD35 which is the uppermost hierarchy data appears as 1/16 line×1/16pixel.

The hierarchical coding encoder unit 40A repeats a recursive processwith respect to the first to the fifth hierarchy data D31 to D35 byturns in the manner that starts with the uppermost hierarchy data (thatis, the fifth hierarchy data D35), and obtains the difference betweenthe adjacent two hierarchy data at the difference circuits 41, 43, 45,and 47. Then, only the difference data is subjected to compressioncoding by the coders 51 to 55. Thus, the quantity of the informationwhich is sent to the transmission line is compressed by the hierarchicalcoding encoder unit 40A. Further, the hierarchical coding encoder unit40A reduces one pixel among the four pixels of the lower hierarchycorresponding to the one pixel of the upper hierarchy by the coders 51to 54 to reduce the transmitting data quantity.

In order to maintain such a compression condition optimally, thehierarchical coding encoder unit 40A decodes the transmission data D51to D55 which has been obtained for each hierarchy by decoders 56 to 59.

The decoder 59 which corresponds to the uppermost hierarchy decodes thetransmission data D55 so as to obtain the decoded data D48, whichcorresponds to the fifth hierarchy data D35 which has beencompression-coded at the coder 55, and outputs the decoded data D48 tothe difference circuit 47 of the fourth hierarchy.

Meanwhile, the other decoders 56 to 58 switch their decoding operationsrespectively, based on a flag which indicates whether thedivision/non-division processing is being performed or not. In the casewhere a division operation is being performed, the difference data whichis to be transmitted as the transmission data D52 to D54 is decoded bythe decoding processing, so that the upper hierarchy data (that is tosay, the fourth, the third, and the second hierarchy data) is generatedand outputted to the difference circuit 45 of the third hierarchy, thedifference circuit 43 of the second hierarchy, or the first hierarchydata 41, respectively.

Hereby, the difference data D41, D42, D43, D44 with respect to theadjacent hierarchies is obtained from the difference circuits 41, 43,45, 47 respectively.

In practice, the decoders 58, 57, 56 are constructed as shown in FIG.13. Here, it will be described as to the decoder 58 for simplification.The decoder 58 receives the fourth hierarchy compression-coded data D54at the decoding circuit 58A to decode it. As a result, the outputvalues, for example, of X1(4)-X1(5), X2(4)-X1(5), X3(4)-X1(5) areobtained that is shown in FIGS. 15(A) to 15(E). These output values areadded to the restored data D48 at the succeeding adding circuit 58B toobtain the output values of the X1(4), X2(4), X3(4). The differencevalue generating circuit 58C generates a non-transmission pixel X4(4)using X1(4), X2(4), X3(4), and X1(5) by performing the calculation basedon Equation (4). Accordingly, the fourth hierarchy data X1(4), X2(4),X3(4), X4(4) before obtaining the difference are generated from thefollowing synthesizing circuit 58D, and these are given to thedifference circuit 45.

The coders 51 to 54 which corresponds to each hierarchy is inputted thedifference data D41, D42, D43, D44, or the fifth hierarchy data D35,which is obtained by the difference circuit 41, 43, 45, 47, or theaveraging circuit 48, and performs a determination between a thresholdvalue and an activity value which is given for each block, and adivision selecting processing.

In the case that the processed object is a block to be divided, thecoders 51 to 54 compression-codes the difference data which has beenobtained between hierarchies as it is, and at the same time, transmitsit along with a determination flag denoting the division of each block.

On the other hand, in the case that the processed object is a block notto be divided, the coders 51 to 54 determine that this block can beswitched by an upper hierarchy data on the receiving side, and exceptthis block from the coding objects. By the way, a determination flagdenoting the division of each block is attached and transmitted in thiscase also.

The first to the fifth hierarchy compression-coded data D51 to D55 whichare outputted from these five sets of coders 51 to 55 are divided intoframes by the predetermined transmission data forming unit (not shown)and sent out to the predetermined transmission lines.

Here, the coders 51, 52, 53, and 54 are constructed as shown in FIG. 14.FIG. 14 shows the structure of the coders 52 and 53 for simplification.

The difference data D42, D43 are inputted to the coding circuits 52A,53A of the coders 52, 53 respectively. The difference data D42, D43 areinputted to the activity detecting circuits 52C, 53C of the divisioncontrol units 52B, 53B respectively. The activity detecting circuits52C, 53C detect the activity of each block of the difference data D42,D43, and thus obtained detected results are given to the followingthreshold value determining circuits 52D, 53D. The threshold valuesdetermining circuits 52D, 53D compare the result of activity detectionfor each block with the threshold value data D57 from the generatedinformation quantity control unit 40B, and output thus obtaineddetermined result to the coding circuits 52A, 53A. The coding circuits52A, 53A compression-code for the block having higher activity andtransmit it, and on the other hand, does not transmit for the blockhaving lower activity.

(2-2) Processing

Next, a concrete signal processing by the hierarchical coding encoderunit 40A will be explained below.

At first, such a situation is considered that a process with respect toan inter-hierarchy difference value is selected by a block activityvalue which is based on the inter-hierarchy difference value. Each blockis composed of 2 lines×2 pixels.

In this situation, the data value of each pixel is denoted by "X", andthe hierarchy of the data value X is represented by attached characters.That is, when an upper hierarchy data is Xi+1(0), the adjacent lowerhierarchy data is Xi(j) (j=0 to 3). The inter-hierarchy difference codedvalue is ΔXi(j) (j=0 to 3), and the hierarchical coding encoder unit 40Acompression-codes this difference coded value.

As to a compression coding process by the coders 51 to 55 at eachhierarchy, a block activity value P which is obtained with respect toeach block and a threshold value data D57 are compared, and then aprocess is selected based on the result of this comparison.

In the case that the block activity value P is the threshold value TH ormore, a division process is sequentially performed with respect to thelower hierarchy. Meanwhile, in the case that the block activity value Pis less than the threshold value TH, the division process with respectto the lower hierarchy is stopped.

Consequently, with respect to a region of which the block activity valueP is low, only the upper hierarchy data is sent, so that the informationquantity which is transmitted can be reduced.

In a region of which the block activity value is low, the picture datadecoding device which receives these data across a transmission line,restores the lower hierarchy data from the upper hierarchy data,utilizing the upper hierarchy data out of the transmission data which issent sequentially. On the other hand, in a region of which the blockactivity value is high, the inter-hierarchy difference decoded value andthe upper hierarchy data are added so that the data is restored.

A determination flag of one bit has been introduced, toward thisdetermined result of a division or a non-division. By virtue of thisflag, the determined result of each block can be indicated.

This determination flag requires one bit per block of each hierarchy,but it is efficient in consideration of the picture quality.

Note that, in the hierarchical coding system of this embodiment, it isassumed that this determination flag is not reflected to thedetermination at the following lower hierarchies. Further, thisdetermination flag is coded by means of the run-length coding or thelike, and transmitted along with the coded code.

(3) Generated Information Quantity Control Unit 40B

(3-1) Structure of Block

The generated information quantity control unit 40B is structured asshown in FIG. 16.

The generated information quantity control unit 40B sets the combinationof threshold values TH1 to TH4 for each hierarchy which is reference onselection of division/non-division, and outputs this to the hierarchicalcoding encoder unit 40A as threshold value data D57, in order that thehierarchical coding encoder unit 40A can efficiently code the picturedata without deteriorating the picture quality.

The generated information quantity control unit 40B generates picturedata of five hierarchies having different resolutions from each other,by 1/4-averaging the input picture data D31 sequentially through theaveraging circuits 42, 44, 46, and 48.

Next, differences between the hierarchical picture data D32, D33, D34,D35 and the picture data D31, D32, D33, D34 of the respectivehierarchies, the former hierarchy being upper than the latter by onehierarchy, are obtained at respective difference circuits 61, 62, 63,64, to obtain the generated information quantity for each hierarchy ofthe picture data transmitted as a difference data.

These difference data outputted from respective difference circuits 61,62, 63, 64 can be defined as a difference data of each hierarchy whichis obtained by the hierarchical processing at the hierarchical codingencoder unit 40A.

The activity detecting circuits 65, 66, 67, 68 correspond to the picturedata of the first to the fourth hierarchies respectively. The activitydetecting circuit 65, 66, 67, 68 obtain the block activity of each blockat the respective hierarchies and register it to the correspondingfrequency tables 69 to 72.

In generating process of the frequency table, three pixels which areobjects to be transmitted by the encoder practically, are used out offour pixels of a lower hierarchy corresponding to one pixel of the upperhierarchy, to grasp correctly the quantity of data to be transmitted ofthe encoder unit.

Since the picture data of the fifth hierarchy is the uppermost hierarchydata, which is transmitted directly not as difference data. Therefore,the dynamic range of each block is registered to the frequency table 73as it is.

The control unit 74 and these five frequency tables 69 to 73 areconnected via bi-directional signal channels. The control unit 74 storescombination of the threshold values TH1 to TH4 and the block activitywhich is a determination reference of the division/non-division of thelower hierarchy in the ROM.

The control unit 74 supplies these combinations to the frequency tables69 to 73 to read out the generated information quantity which may begenerated for the above threshold value for each hierarchy, and then thetotal generated information quantity is obtained based on all of thetotal generated information quantity as a whole. Then, the optimalthreshold value is obtained until the total generated informationquantity reaches the target value, and thus obtained threshold value isgiven to the hierarchical coding encoder unit 40A as a control data.

Further, the control unit 74 adjusts the control data to be supplied tothe hierarchical coding encoder unit 40A for each hierarchy, consideringthe characteristic of picture signal data, the visual characteristics ofhuman being, and the like, so that the optimum threshold value can begiven. Thereby, the picture quality of the picture which is reproducedat the receiving side can be improved subjectively.

(3-2) Frequency Table

Here, it will be described about the frequency tables 69 to 73 forcontrolling information quantity.

FIGS. 17(A) to 17(E) show respectively a frequency table of the blockactivities which are obtained with respect to the uppermost hierarchydata (the fifth hierarchy data) to the lowermost hierarchy data (thefirst hierarchy data). Here, with respect to the frequency table of thefifth hierarchy shown in FIG. 17(A), a frequency table by dynamic rangeis generated because the object data is not difference data. Forinstance, when compression processing by the PCM coding is performed forthe fifth hierarchy data D35, a dynamic range which is given withrespect to each block is registered as a data, and when the ADRC(adaptive dynamic range coding (USP-4703352)) is applied as acompression processing method, "DR" of the ADRC block is registered.

Meanwhile, in the other frequency tables 69 to 72, the object data isdifference data, therefore, a block having the block activity largerthan the threshold values TH1, TH2, TH3, TH4 which are given withrespect to each frequency table is to be a block to be divided.

Accordingly, the generated information quantity can be calculated bycalculating the number of blocks having the block activity larger thanthe threshold value in each hierarchy.

Next, an example of calculation of the generated information quantitywill be described below.

Here, assuming that the number of blocks in the first hierarchy as N1,the number of blocks to be divided of which the block activity is largerthan the threshold value TH1 as N1', and the number of quantization bitsat that time as Q1, then the generated information quantity I1 in thefirst hierarchy is given by the following equation:

    I1=4·Q1·N1'·(3/4)+N1            (7)

In the first term of Equation (7), each number of bits is quadrupled,because in the case of this example, each block is divided into 2lines×2 pixels. Further, in the first term, it is multiplied by 3/4,because the characteristic is reflected that, in a structure that anupper hierarchy value is generated based on the mean value of lowerhierarchy values, the fourth non-transmission pixel value of lowerhierarchy can be restored by means of an arithmetic equation using theupper hierarchy value and three pixels of the lower hierarchy value.

By the way, in the second term, N1 is added to the number of blocks inthe first hierarchy. It means that the respective block is transmittedwith adding one bit as a division determination flag.

Similarly, as to the second, the third, the fourth hierarchy, assumingthat the number of blocks in each hierarchy as N2, N3, N4, the number ofblocks to be divided of which the block activity is larger than thethreshold values TH2, TH3, TH4 as N2', N3', N4', and the number ofquantization bits at that time as Q2, Q3, Q4, then the generatedinformation quantity Ik (k =2, 3, 4) in each hierarchy is given by thefollowing equation:

    Ik=4·Qk·Nk'·(3/4)+Nk            (8)

By using the generated information quantities I1 to I4 of the first tothe fourth hierarchies and the generated information quantity I5 of thefifth hierarchy, the total generated information quantity I which isgenerated by the coding processing of the hierarchical coding encoderunit 40A can be obtained as the sum of generated information quantitiesof each hierarchy as the following equation:

    I=I1+I2+I3+I4+I5                                           (9)

(3-3) Processing

The generated information quantity control unit 40B input an inputpicture data D31 similarly to the hierarchical coding encoder unit 40A,and a mean value is obtained for each 2 lines×2 pixels at the averagingcircuit 42, to reduce the number of pixels into 1/4 and lower theresolution. Similarly, with respect to the hierarchy data D32, thenumber of pixels is reduced into 1/4 and lowered the resolution bysequentially passing the averaging circuits 43, 46, 48.

The generated information quantity control unit 40B gives the uppermosthierarchy data D35 (i.e., having the lowest resolution) to the frequencytable 73 out of picture data having a plurality of resolutions, and thefrequency of the block activtivity P of each block in the fifthhierarchy data D35 is registered. This is measurement of the frequencyof data which corresponds to the compression processing performed at theabove hierarchical coding encoder unit 40A. For instance, when thecompression processing by the PCM coding is performed for the fifthhierarchy data D35, a dynamic range which is given for each block isregistered as a data, and on the other hand, when the ADRC is applied asa compression processing, "DR" of the ADRC block is registered.

The difference data D64 can be obtained by the difference between thefourth hierarchy data D34 and the fifth hierarchy data D35. The activitydetecting circuit 68 detects the activity with respect to the differencedata D64, and nd registers it to the frequency table 72 as the activitydata D68.

Similarly, the block activity P of each block which is obtained withrespect to the respective lower hierarchy data D33, D32, D31 issequentially registered to the frequency tables 71, 70, 69 as theactivity data D67, D66, D65.

The control unit 74 sequentially reads out the combination with respectto the threshold values TH1, TH2, . . . TH4 for settingdivision/non-division which is set for each hierarchy from the ROM tableshown in FIG. 18 in order from the group of youngest number (Q_(NO1)).Continuously, the block frequency having the block activity value Pwhich is larger than respective threshold values TH1, TH2, . . . TH4 isread out from the frequency tables 69 to 73 for each hierarchy, todetect the generated information quantity for each threshold value withrespect to each hierarchy.

The control unit 74 integrates the generated information quantity whichis obtained with respect to the frequency tables 69 to 73 of eachhierarchy, and calculates the total generated information quantity whichwill be generated by coding at the hierarchical coding encoder 40A. Thecontrol unit 74 compares this generated information quantity ay and thetarget value, and when the difference is large, it proceeds to the groupof the threshold values TH1, TH2, . . . TH4 of the next number (Q_(N)02) to obtain a combination of the threshold values which satisfies thetarget value.

Hereinafter, the above processing is repeated until achieving the totalgenerated information quantity to the target value, and a group of thethreshold values TH1, TH2, . . . TH4 in which the total generatedinformation quantity nearest to the target value can be obtained isobtained, to output this to the hierarchical coding encoder 40A as thethreshold value data D57.

According to the above structure, the coding of hierarchies having aplurality of resolutions can be easily realized. Further, the totalgenerated information quantity of transmission picture data which iscoded and outputted from the hierarchical coding encoder 40A can almostbe equaled to the target value, thereby the coding in which thecompression efficiency does not lower can be realized. Further, thehierarchical coding can be realized with less deterioration of thepicture quality. Furthermore, the management of generated informationquantity in the hierarchical coding can be more simplified comparingwith the conventional one.

(4) Other Embodiments of Third Embodiment

(4-1) In the embodiment described above, such a case is described thatthe block activity value P is determined based on the decoded dataobtained for each block with respect to the upper hierarchy data and themaximum value of the difference value between the lower hierarchy data.However, the present invention is not only limited to this, but thedetermination can be performed based on an average error, an absolutevalue sum, a standard deviation, an n-th power sum, or a frequency ofdata which is a threshold value or more in a block.

(4-2) In the embodiments described above, such a case is described thatthe frequency table obtained for each hierarchy is used as it is.However, the present invention is not only limited to this, but can usean integrating frequency table which is produced based on the frequencytable for calculation of the generated information quantity.

More specifically, assuming that the frequency table as shown in FIG. 19is obtained as a result of registering the block activity value, anintegrating operation is performed on the values which is lower than thefrequency corresponding to the maximum value of the block activityvalue, and the respective results are registered to the integratingfrequency table as shown in FIG. 20.

Assuming the value of block activity (k=0 to the maximum value) as "k",and a block frequency in each block activity value as N(·), thisprocessing is represented by the following equation:

    N(k-1)=N(k-1)+N(k)                                         (10)

This equation means that the result, that the block frequency of addressof a block activity value is read and added to the integrated valueuntil the upper block activity value, is written into the address of theblock activity value.

In the integrating frequency table (FIG. 20) thus obtained as a result,the sum of block frequencies of the hatched portion in FIG. 19correspond to a threshold value TH coordinate data I in the hatchedportion. By virtue of this integrating frequency table, it becomeunnecessary to calculate the sum of block frequencies of the hatchedportion (FIG. 19) every time.

More specifically, an accumulated and added value is obtained withrespect to block frequencies from the value upper than block activityvalue to the value of each block activity, and each accumulated andadded value is written into the address which corresponds to the valueof each block activity so as to produce an integrating frequency table,thereby a frequency corresponding to each block activity becomes anintegrated value of the block frequency which has the value of the blockactivity or more.

Calculation of block frequency integrated value which corresponds toeach threshold value is to be unnecessary, by producing an integratingfrequency table previously as described above, and a block frequencyintegrated value can be calculated by only reading out a thresholdaddress of memory. Thereby, a time requires for calculation can bewidely shortened.

Here, in practical threshold value processing, it is difficult to use alarge determination threshold value because picture qualitydeteriorates. Accordingly, a frequency table in which the block activityvalue is clipped can be formed.

That is, all of block frequencies larger than or equal to the above LMTis registered into the LMT in a frequency table as shown in FIG. 21,when the block activity value is clipped by the LMT. As a result, theblock frequency in the LMT become large as shown in FIG. 21. Here, sumof block frequencies to be calculated is the hatched portion.

FIG. 22 shows an integrating frequency table contrary to this frequencytable. In this case, the integrating calculation of Equation (10)described above is not by the maximum value of block activity value andis performed for a period from the block activity value to 0. The sum ofblock frequencies to be calculated is an integrated block frequency I ofcoordinates of the threshold value TH. In this manner, the same resultas the case shown in FIG. 20 can be obtained.

Thereby, a time for producing an integrating frequency table can beshortened and a table frequency memory can be more miniatulized.

By the way, it is considered that a method for changing the clippedvalue LMT for each hierarchy as the first method, and a method forsetting the clipped value LMT to a fixed value in all of hierarchies asthe second method. The first method is used in the case where thedistributions of inter-hierarchy difference values of each hierarchy aredifferent from each other clearly. The second method is used in the casewhere the distributions of inter-hierarchy difference of each hierarchyis almost the same from each other.

Further, in the embodiments described above, such a case is describedthat the picture data is PCM coded at the coder. However, the presentinvention is not only limited to this, but the other coding schemes,such as an orthogonal coding scheme, can be applied.

Further, in the embodiments described above, such a case is describedthat the plural combinations of the threshold value of the frequencytable which has been obtained for each hierarchy are previously storedin a ROM, and then the combination of the threshold value by which thegenerated information quantity becomes nearest to the target value isobtained. However, the present invention is not only limited to this,but is possible to be adapted to set it independently for eachhierarchy.

Further, in the embodiments described above, such a case is describedthat the lowermost hierarchy data is averaged for each 2 lines×2 pixelsat a time so that the picture data of the upper hierarchy is obtained,however, the present invention is not only limited to this, but theaverage value may be obtained by other combinations.

(5) As described above, according to the present invention, when apicture data is sequentially and recursively divided and coded into theplural hierarchy data having a plurality of different resolutions, theblock activity value is determined with respect to the predeterminedblock of the hierarchy data excepting the uppermost hierarchy datahaving a lowest resolution, and then the threshold value which is thedetermination standard of the division process to the lower hierarchydata is set from the frequency distribution of the block correspondingto the block activity value. Thereby, the method for hierarchicallycoding the picture data can be realized without lowering the compressionefficiency can be easily realized.

5! Fourth Embodiment

(1) Picture Coding Apparatus of Fourth Embodiment

A picture coding apparatus 80 of the fourth embodiment has the sameschematic construction as a case of the third embodiment (FIG. 11) asshown in FIG. 23, and is composed of a hierarchical coding encoder unit80A which hierarchically codes an inputted picture data D1 and outputsit, and a generated information quantity control unit 80B which controlsthe generated information quantity in the hierarchical coding encoderunit 80A so that it attains the target value.

The hierarchical coding encoder unit 80A is composed of a data delayingmemory (not shown) and an encoder. The memory is provided in theinputting stage in order that the data can be delayed so that theencoding process will not be performed until an optimal control value isdetermined in the generated information quantity control unit 80B.

Meanwhile, the generated information quantity control unit 80B isadapted to be inputted an input picture data D31 and then determines athreshold value TH which is accommodated to the data to be processed,and also adapted to transmit the optimal control value, which isdetermined so that the inputted picture data D31 will be efficientlycoded in the hierarchical coding encoder unit 80A, to the encoder. Ithas a construction of a so-called feed-forward type buffering. By virtueof this construction, the accurate control of the generated informationquantity can be performed and a time delay generated by the feed-forwardtype buffering can be eliminated.

Hereupon, the selection of the division processing in the lowerhierarchy is performed, by a block activity value which is defined basedon the difference value between hierarchies. From four pixels of 2×2 ofthe lower hierarchy, the upper hierarchy data is composed and a block isdefined.

Here, activity is a correlation value which is represented by a maximumvalue, a mean value, an absolute value sum, a standard deviation, or ann-th power sum, etc., of inter-hierarchy difference data D41 to D44 in apredetermined block, in the case of defining a lower hierarchy data areacorresponding to an upper hierarchy data as "block". That is, when theactivity is low, it can say that this block is a plane block.

Denoting an upper hierarchy data by XO(i+1) and a lower hierarchy databy Xj(i), an inter-hierarchy difference coded value ΔXj(i) becomes equalto ΔXj(i)=XO(i+1)-Xj(i), where j=0 to 3. Meanwhile, denoting a blockactivity value determining function by G(·), a block activity value ACTis described as ACT=G(ΔXj(i)).

Further, denoting a hierarchy determination flag by FLG (0:divisionstop, 1:division continue), when FLG=0, the division of the lowerhierarchy is stopped, when ACT≧threshold value TH and FLG=1, thedivision of the lower hierarchy is performed, and when ACT<thresholdvalue TH and FLG=1, the division of the lower hierarchy is stopped.

After the division determination is terminated in this hierarchy, thedivision determined result is defined as a determination flag FLG,thereafter, it is transmitted to the next lower hierarchy. As the above,the division in the lower hierarchy is not performed when FLG=0.

(2) Hierarchical Coding Encoder Unit

The hierarchical coding encoder unit 80A has the construction shown inFIG. 24, and has the same construction as that is described with respectto FIGS. 12 and 13, excepting a point that coders 51 to 54 arestructured as shown in FIG. 25.

The coders 54, 53, 52 in this case output respectively threshold valuedetermined result information J1, J2, J3 which has been used in divisionor non-division of the block to the coders 53, 52, 51 of the lowerhierarchy which is adjacent thereto. Thereby, the hierarchical codingencoder unit 80A stops all of division with respect to the block inwhich the block division has been stopped once, in the following lowerhierarchies.

Practically, the coders 51 to 54 are structured as shown in FIG. 25.FIG. 25 shows the structure of the coders 52 and 53 for simplification.

The coder 53 inputs a difference data D43 to the coding circuit 53A andthe activity detecting circuit 53C of the division control unit 53B. Theactivity detecting circuit 53C detects an activity for each specifiedblock of the difference data D43, and gives thus obtained detectedresult to the following threshold value determining circuit 53D. Thethreshold value determining circuit 53D compares the detected result ofactivity for each block and the threshold value data D57, and outputsthus obtained determined result to the coding circuit 53A and theadjacent coder 52 of the lower hierarchy as the threshold valuedetermined result information J2. The coding circuit 53Acompression-codes and transmits with respect to a block having highactivity, on the contrary, does not transmit with respect to a blockhaving low activity, according to the threshold value determined resultinformation J2.

Here, the activity detecting circuit 53C and the threshold valuedetermining circuit 53D receive the threshold value determined resultinformation J1 which is outputted from the adjacent coder 54 of theupper hierarchy, so that the activity detection and the threshold valuedetermined result are performed in the case where the threshold valuedetermined result information J1 is that represents to perform divisionof the block. On the contrary, the activity detection and the thresholdvalue determination are not performed with respect to the correspondingblock in the case where the threshold value determined resultinformation J1 is that represents non-division of the block, and thethreshold value determined result information J2 which representsnon-division of the block is outputted from the threshold valuedetermining circuit 53D. The coder 52 also performs activity detectionand threshold value determination with respect to the correspondingblock, in the case where the activity detecting circuit 52C and thethreshold value determining circuit 52D receive the threshold valuedetermined result information J2 which represents division of the blockfrom the adjacent coder 53 of the upper hierarchy. On the contrary, inthe case where the threshold value determined result information J2which represents non-division of the block, the coder 52 does notperform activity detection and threshold value determination, andoutputs the threshold value determined result information J3 whichrepresents non-division of the block from the threshold valuedetermining circuit 52D.

As the above, in the hierarchical coding encoder unit 80A, ifnon-division determined result has been obtained once, the blockdivision is not performed (i.e., is not coded) with respect to thecorresponding block in the following lower hierarchies.

(3) Generated Information Quantity Control Unit

The generated information quantity control unit 80B is structured suchas shown in FIG. 26.

The generated information quantity control unit 80B generates picturedata of five hierarchies having different resolutions from each other,by 1/4-averaging the input picture data D31 sequentially through themean value circuits 42, 44, 46, and 48.

Next, differences between the hierarchical picture data D32, D33, D34,D35 and the picture data D31, D32, D33, D34 of the respectivehierarchies, the former hierarchy being upper than the latter by onehierarchy, are obtained at respective difference circuits 61, 62, 63,64, to obtain the generated information quantity for each hierarchy ofthe picture data transmitted as a difference data.

These difference data outputted from respective difference circuits 61,62, 63, 64 can be defined as a difference data of each hierarchy whichis obtained by the hierarchical processing at the hierarchical codingencoder unit 80A.

The activity detecting circuits 65, 66, 67, 68 correspond to the picturedata of the first to the fourth hierarchies respectively. The activitydetecting circuit 65, 66, 67, 68 obtain the activity of each block withrespect to the respective hierarchies and register it to thecorresponding frequency tables 69 to 72.

In generating process of the frequency table, three pixels which areobjects to be transmitted by the encoder practically, are used out offour pixels of a lower hierarchy corresponding to one pixel of the upperhierarchy, to grasp correctly the quantity of data to be transmitted ofthe encoder unit.

Since the picture data of the fifth hierarchy is the uppermost hierarchydata, which is transmitted directly not as difference data. Therefore,the dynamic range of each block is registered to the frequency table 73as it is.

This measure the frequency of data corresponding to the compressionprocessing which is performed in the encoder unit 80A described above.For instance, when compression processing by the PCM coding is performedfor the fifth hierarchy data D35, a dynamic range which is given withrespect to each block is registered as a data, and when the ADRC(adaptive dynamic range coding (U.S. Pat. No. 4,703,352)) is applied asa compression processing method, "DR" of the ADRC block is registered.

Succeedingly, the difference data D64 is generated from the fourthhierarchy data D34 and the fifth hierarchy data D35. As to thedifference data D64, its block activity is detected at the activitydetecting circuit 68. The detected block activity D68 is registered tothe frequency table 72.

The difference data D63 is generated from the third hierarchy data D33and the fourth hierarchy data D34. As to the difference data D63, itsblock activity is detected at the activity detecting circuit 67. Thedetected block activity D67 is registered to the frequency table 71. Atthis time, block division determination is performed in the thirdhierarchy only with respect to the block that is received thedetermination of block division continue in the threshold valuedetermined result in the fourth hierarchy.

Accordingly, the frequency table 71 shows the number of blocks of whichthe coordinates is determined by two variables of the block activityvalue D68 in the fourth hierarchy and the block activity value D67 inthe third hierarchy.

Further, the difference data D62 is generated from the second hierarchydata D32 and the third hierarchy data D33, and the block activity valueD66 is outputted at the activity detecting circuit 66. The detectedblock activity value D66 is registered to the frequency table 70. In thesecond hierarchy, determination of block division is performed only withrespect to the block that is received the determination of divisioncontinue in the fourth and the third hierarchies.

Accordingly, the frequency table 70 is to be a block frequency table ofwhich the coordinates is determined by three variables of the blockactivity value D68 in the fourth hierarchy, the block activity D67 inthe third hierarchy, and the block activity value D66 in the secondhierarchy.

Lastly, the difference data D61 is generated from the first hierarchydata D31 and the second hierarchy data D32, and the block activity valueD65 is outputted at the activity detecting circuit 65. The detectedblock activity value D65 is registered to the frequency table 69. In thefirst hierarchy, determination of block division is performed only withrespect to the block which is received the determination of blockdivision continue in the fourth, the third, and the second hierarchies.

Accordingly, the frequency table 69 is composed of four variables of theblock activity value D68 in the fourth hierarchy, the block activityvalue D67 in the third hierarchy, the block activity value D66 in thesecond hierarchy, and the block activity value D65 in the firsthierarchy.

The control of generated information quantity is performed using thusgenerated frequency tables 69 to 73. Each frequency table and thecontrol unit 74 of the latter stage are connected each other withbi-directional signal channels D69 to D73.

In the control unit 74, a threshold value with respect to each frequencytable is transmitted to each frequency table. In each frequency table ,the generated information quantity corresponding to the threshold valueis detected. The generated quantity in each frequency table istransmitted via the signal channels D69 to D73 to the control unit 74.

In the control unit 74, the total generated information quantity to becontrolled is calculated by integrating the received generatedinformation quantity in each frequency table. This total generatedinformation quantity and the target value are compared, and thethreshold value is changed according to the comparison result so thatthe target value is satisfied.

The threshold value updated again is transmitted from the control unit74 via the signal channels D69 to D73 to each frequency table. Further,the generated information quantity corresponding to the threshold valueis transmitted again to the control unit 74.

The above processing is repeated, and the control result D57 forattaining the target value is determined finally. The detected generatedinformation quantity control value D57 is transmitted to thehierarchical coding encoder unit 80A.

The data to be controlled is waited into a memory M1 which is includedin the encoder unit 80A while this generated information quantitycontrol processing. The threshold value applied to the object data canbe determined by using the structure of feed-forward type buffering, asa result, the coding can be realized with high efficiency.

Here, it will be described that frequency tables 69 to 73 forinformation quantity control below.

FIGS. 27(A) to 27(E) show respectively a frequency table of the blockactivities which has been obtained with respect to the uppermosthierarchy data (the fifth hierarchy data) to the lowermost hierarchydata (the first hierarchy data). As to the frequency table of the fifthhierarchy shown in FIG. 27(A), since the difference data is not anobject data, the frequency table by dynamic range is generated. Forinstance, the dynamic range with respect to the coded block isregistered in case of applying the PCM coding.

Meanwhile, in the another frequency tables 69 to 72, the object data isa difference data, and a block having the block activity value largerthan or equal to the threshold values TH1, TH2, TH3, TH4 which are givenwith respect to each frequency table is to be a block to be divided.

Accordingly, the generated information quantity can be calculated bycalculating the number of blocks having the block activity larger thanor equal to the threshold value in each hierarchy.

Next, an example of calculation of the generated information quantitywill be described below. To calculate the generated informationquantity, it is needed to count the number of blocks which is largerthan or equal to the division determination threshold value in eachhierarchy. However, in the control of the generated information quantityin the hierarchical coding by determination flag propagating methodwhich is objected in this embodiment, it is needed to eliminate theblock, which received the determination of division stop in the upperhierarchy, from the determination object in the lower hierarchy.

Further, in each hierarchy, a threshold value for the block activity isintroduced to perform division determination.

Here, assuming that the sum of pixel numbers in the block to be dividedin the first hierarchy as Ml, the number of quantization bits of thefirst hierarchy data as Q1, the number of determination flag bits of thefirst hierarchy as N1, then the generated information quantity I1 in thefirst hierarchy is given by the following equation:

    I1=4·Q1·M1·(3/4)+N1             (11)

In the first term of Equation (11), each number of bits is quadrupled,because in the case of this example, each block is divided into 2lines×2 pixels. Further, in the first term, it is multiplied by 3/4,because the characteristic is reflected that in a structure that anupper hierarchy value is generated based on the mean value of lowerhierarchy values, the fourth non-transmission pixel value of lowerhierarchy can be restored by means of an arithmetic equation using theupper hierarchy value and three pixels of the lower hierarchy value.

By the way, in the second term, Nl is added to the number of blocks inthe first hierarchy, it means that the respective blocks are transmittedwith adding one bit as a division determination flag.

Similarly, as to the second, the third, the fourth hierarchy, assumingthat the sum of pixel numbers in the block to be divided in eachhierarchy as M2, M3, M4, the number of quantization bits in eachhierarchy as Q2, Q3, Q4, the number of determination flag bits in eachhierarchy as N2, N3, N4, then the generated information quantity Ik(k=2, 3, 4) in each hierarchy is given by the following equation:

    I=I1+I2+I3+I4+I5                                           (12)

Using the generated information quantities I1 to I4 of the first to thefourth hierarchy and the generated information quantity I5 of the fifthhierarchy, the total generated information quantity I which is generatedby the coding processing of the hierarchical coding encoder unit 80A canbe obtained as a sum of generated information quantities for eachhierarchy as the following equation:

    Ik=4·Qk·Mk·(3/4)+Nk             (13)

Here, the number of bits of the determination flag is added to thegenerated information quantity of each hierarchy. However, theinformation quantity of this flag is equal to the number of blocks whichhas been performed the division processing in the upper hierarchy. Thatis, it means that the block in which the division processing has beenstopped in the upper hierarchy is eliminated from the divisiondetermination object in the lower hierarchy. The spatial position ofeach block can be specified in each hierarchy by a history of thedetermination flag from the upper hierarchy.

Now, the individual frequency tables will be explained.

As stated above, since the frequency table of the upper hierarchy datadepends on the compression scheme, it is not determined uniquely.However, the generated information quantity can be controlled usingmeans such as a frequency table.

Next, as to the fourth hierarchy data, the block frequency toward theblock activity value ACT4 is registered. By applying the fourthhierarchy frequency table of FIG. 28(B) to the fifth hierarchy frequencytable of FIG. 28(A), the generated information quantity which is relatedto the threshold value TH4 can be easily calculated.

Since the blocks which are larger than or equal to the threshold valueTH4 are the object of division, the generated information quantity onthe fourth hierarchy is calculated by computing the sum of the number ofblocks which are not less than the threshold value.

Next, an example of the frequency table of the third hierarchy is shownin FIG. 29. In the determination flag propagating scheme, the blockswhich have been received the determination of division stopping at theupper hierarchy are eliminated from the determination object.

Then, such a frequency table is introduced that is defined by twovariables of the third hierarchy block activity value ACT3 and thefourth hierarchy block activity value ACT4.

In other words, such a block frequency is obtained that is larger thanor equal to the threshold value TH4 of the fourth hierarchy and largerthan or equal to the threshold value TH3 of the third hierarchy.

As to this operation, by calculating the block frequency which is largerthan or equal to the threshold value TH4 at the ACT4 axis and largerthan or equal to the threshold value TH3 at the ACT3 axis on thefrequency table of FIG. 29, the generated information quantity in thethird hierarchy which satisfies the above conditions can be calculated.

Next, the examples of the frequency tables for the second hierarchy andthe first hierarchy are shown in FIG. 30.

In accordance with the same idea as that of the frequency table of thethird hierarchy, a frequency table which is defined by several variablesis produced.

In the second hierarchy, the blocks which are defined by the respectiveblock activities ACT2, ACT3, and ACT4 of the second hierarchy, the thirdhierarchy, and the fourth hierarchy are registered to the frequencytable. This situation is shown in FIG. 30(A).

In the second hierarchy, by calculating the block frequency which islarger than or equal to the threshold value TH4 at the ACT4 axis, largerthan or equal to the threshold value TH3 at the ACT3 axis, and largerthan or equal to the threshold value TH2 at the ACT2 axis, the generatedinformation quantity in the second hierarchy is calculated.

In the first hierarchy, the blocks which are defined by the respectiveblock activities ACT1, ACT2, ACT3, and ACT4 of the first hierarchy, thesecond hierarchy, the third hierarchy, and the fourth hierarchy areregistered to the frequency table. This situation is shown in FIG.30(B).

In the case of the first hierarchy, by calculating the block frequencywhich is larger than or equal to the threshold value TH4 at the ACT4axis, larger than or equal to the threshold value TH3 at the ACT3 axis,and larger than or equal to the threshold value TH2 at the ACT2 axis,the generated information quantity in the first hierarchy is calculated.

The generated information quantity toward the threshold value can becalculated utilizing the abovementioned five kinds of frequency tables,and can be controlled so as to coincide with the target informationquantity.

As to the threshold value of each hierarchy which is utilized to controlthe generated information quantity, there are methods for changing itindependently for each hierarchy.

For instance, there is such a scheme that the target informationquantity is previously set for each hierarchy and then the thresholdvalue is independently changed for each hierarchy, so that it iscontrolled so as to coincide with the target information quantity.

Also, as another scheme, such a scheme that the combinations of thethreshold values for each hierarchy are previously prepared, and thenthese threshold value sets are applied in accordance with a controlsequence can be also considered, and thereby the control is simplified.

In the abovementioned scheme for controlling the generated informationquantity which utilizes the frequency table of each hierarchy, in eachhierarchy, the block frequency whose block activity value at eachhierarchy is larger than or equal to the threshold value, is calculatedconsidering the division determined result of the upper hierarchy, sothat the optimal control value is detected.

In order to shorten the time for calculating the block frequency whichis larger than or equal to the threshold value, the frequency table inwhich the block frequency is registered may be reconstructed into anintegration type frequency table.

An example of this integrating frequency table is shown in FIG. 32. Itis supposed that a block activity value has been registered with theresult that an example of a frequency table which is shown in FIG. 31has been obtained. In this case, to simplify the explanation, an exampleof which the block activity value is one variable is shown. In theabovementioned frequency table, it is the same one as that of the fourthhierarchy.

The integrating frequency table has such a structure that theintegrating calculation is performed, starting from the block frequencywhich corresponds to the maximum value of the block activity value ofthe frequency table of FIG. 31, and toward the block frequency whichcorresponds to the smaller block activity value, so that the respectiveresults of the integration are re-registered in the frequency table.

This process is represented as the following equation: ##EQU1## Here,"SUM(·)" represents a integrated block frequency, "N(·)" represents ablock frequency in a frequency table, "act" denotes a block activityvariable in the integrating frequency table, "ACT" denotes a blockactivity variable in the frequency table, and "n" denotes the maximumvalue of a variable in the frequency table.

What is meant by Equation (14) is such a process that a block frequencyof a block activity value address is read and added to the integratedvalue which has been obtained up to the upper block activity value, andthen the result is written into the present block activity valueaddress.

As a result, the integration type frequency table which is shown in FIG.32 is obtained. In this integrating frequency table, the sum of theblock frequency of the hatched portion of FIG. 31 corresponds to thethreshold value TH coordinate data I.

By virtue of this integrating frequency table, it becomes unnecessary tocalculate the sum of the block frequency of the hatched portion of FIG.31 each time the threshold value TH is changed. That is to say, byoutputting the integrated block frequency which corresponds to thethreshold value of the integrating frequency table, the calculation ofthe sum of the block frequency is realized.

Also, the third hierarchy frequency table of FIG. 29 shows the case oftwo variables. By expanding Equation (14), an integrating frequencytable is produced and the following equation: ##EQU2## is obtained.Here, "SUM(·)" represents an integrated block frequency, "N(·)"represents a block frequency in a frequency table, "act3" denotes thethird hierarchy corresponding variable in an integrating frequencytable, "act4" denotes the fourth hierarchy corresponding variable in theintegrating frequency table, "ACT3" denotes the third hierarchy variablein the frequency table, "ACT4" denotes the fourth hierarchy variable inthe frequency table, and "n" denotes the maximum value of the variablein the frequency table.

In an integrating frequency table which is produced in accordance withEquation (15), an integrated block frequency which corresponds to theaddress of the determination threshold value TH3 of the third hierarchyand the determination threshold value TH4 of the fourth hierarchyindicates the sum of the block frequency which is larger than or equalto the threshold value TH3 and also larger than or equal to thedetermination threshold value TH4. In this way the generated informationquantity at the third hierarchy can be calculated.

With respect to the frequency tables of the second hierarchy and thefirst hierarchy shown in FIG. 30, the time for calculating the blockfrequency sum can also be shortened by utilizing an integratingfrequency table.

In these cases the number of block activities increases, therefore thenumber of integration increases.

First, the operational expression in the case of the second hierarchy isrepresented by the following equation: ##EQU3## Here, "SUM(·)"represents a integrated block frequency, "N(·)" represents a blockfrequency in a frequency table, "act2" denotes the second hierarchycorresponding variable in an integrating frequency table, "act3" denotesthe third hierarchy corresponding variable in the integrating frequencytable, "act4" denotes the fourth hierarchy corresponding variable in theintegrating frequency table, "ACT2" denotes the second hierarchyvariable in the frequency table, "ACT3" denotes the third hierarchyvariable in the frequency table, and "ACT4" denotes the fourth hierarchyvariable in the frequency table.

In the integrating frequency table which is produced in accordance withEquation (16), the integrated block frequency which corresponds to theaddress of the determination threshold value TH2 of the second hierarchyand the determination threshold value TH3 of the third hierarchy and thedetermination threshold value TH4 of the fourth hierarchy indicates thesum of the block frequency which is larger than or equal to thethreshold value TH2 and also larger than or equal to the threshold valueTH3 and also larger than or equal to the determination threshold valueTH4.

In this manner, the generated information quantity in the secondhierarchy can be calculated.

Lastly, a process which is related to the frequency table of the firsthierarchy shown in FIG. 30(B) will be described.

In this case, there are four kinds of block activity value variables,therefore the number of integrating calculations becomes the most. Theoperational expression in the case of the first hierarchy is representedby the following equation: ##EQU4## Here, "SUM(·)" represents anintegrated block frequency, "N(·)" represents a block frequency in afrequency table, "act1" denotes the first hierarchy correspondingvariable in an integrating frequency table, "act2" denotes the secondhierarchy corresponding variable in the integrating frequency table,"act3" denotes the third hierarchy corresponding variable in theintegrating frequency table, "act4" denotes the fourth hierarchycorresponding variable in the integrating frequency table, "ACT1"denotes the first hierarchy variable in the frequency table, "ACT2"denotes the second hierarchy variable in the frequency table, "ACT3"denotes the third hierarchy variable in the frequency table, and "ACT4"denotes the fourth hierarchy variable in the frequency table.

In the integrating frequency table which is produced in accordance withEquation (17), the integrated block frequency, which corresponds to theaddress of the determination threshold value TH1 of the first hierarchyand the determination threshold value TH2 of the second hierarchy andthe determination threshold value TH3 of the third hierarchy and thedetermination threshold value TH4 of the fourth hierarchy, indicates thesum of the block frequency which is larger than or equal to thethreshold value TH1, larger than or equal to the threshold value TH2and, larger than or equal to the threshold value TH3, and also largerthan or equal to the threshold value TH4. In this manner, the generatedinformation quantity at the first hierarchy can also be calculated.

As a result of this process, the calculation of the generatedinformation quantity based on the number of the dividing object blocksin each hierarchy based on Equation (12) is realized.

By the introduction of the above described integrating frequency table,the time for controlling the generated information quantity can beshortened significantly. Such a method will be described below that thetime for controlling the generated information quantity is furthershortened on this integrating frequency table.

The integrating frequency table which is used in this proposal isutilized to calculate the information quantity which is generated towardthe division determination threshold value. In the actual thresholdvalue processing, a large determination threshold value can not bepractically used, from the viewpoint of the degradation of the picturequality. Hence, it is proposed herein to make frequency tables whoseblock activity value is clipped. Such a situation is shown in FIGS. 33and 34.

As shown in FIG. 33, on the condition that the block activity value isclipped at LMT, the block frequency which are larger than or equal toLMT are all registered as LMT to the frequency table. As a result, theblock frequency at LMT become large, as indicated in the figure. Theblock frequency sum to be calculated is the hatched portion.

The integrating frequency table toward this frequency table is shown inFIG. 33. The integrating calculations which are shown in Equations (14)to (17) are performed with respect to the interval, which extends fromthe block activity value LMT instead of the maximum value "n" of theblock activity value, to "0".

The block frequency sum to be calculated is the integrated blockfrequency I of the coordinate of the threshold value TH. As shown inthis example, the same result as that of FIG. 32 is obtained. By theintroduction of clipping into the block activity value of the frequencytable, a shortening of the integrating frequency table generating timeand a miniaturization of the frequency table memory space can berealized.

As the frames to which this scheme is applied, two frames can beconsidered. One of these is the case where clipping value LMT is changedfor each hierarchy, and the other is the case where clipping value LMTis fixed for all hierarchies.

The former is utilized when there are clear differences in thedistribution of the inter-hierarchy difference values of each hierarchy,and the latter is utilized when there are little differences in thedistribution of the inter-hierarchy difference values of each hierarchy.

Note that, FIG. 35 shows a flowchart of the hierarchical coding process.In the step SP2, "4" is registered in the hierarchy counter I forstoring the hierarchy number, so that the frame of this hierarchizationis determined.

Further, at step SP3, the hierarchical data is produced by the generatedinformation quantity calculation, and at step SP4, each block activityvalue is detected. With respect to this activity value, at step SP5, themulti-dimensional frequency table which is abovementioned in relation toFIG. 29 is generated and registered, hereby the generated informationquantity controlling is performed and the optimal control value isdetermined.

Further, at step SP6, the hierarchical coding is performed at theencoder side based on this control value. At first, the coding and thecoding are performed with respect to the data of the fifth hierarchywhich is the uppermost hierarchy. The result of this process becomes tothe initial value of the process at the lower hierarchy, and theinter-hierarchy difference value between this result and the lowerhierarchy is produced at step SP7. Further, at step SP8, based on thegenerated information quantity control value which is determined at theupper stage, the division selecting and the coding at the lowerhierarchy are performed.

After the processing of each hierarchy, the hierarchy counter I isdecremented at step SP9. And then, at step SP10, a terminationdetermination is performed with respect to the content of the hierarchycounter I. In the case where it is not to be terminated, the process ofthe lower hierarchy is further continued. In the case where theprocesses of all hierarchies have been terminated, the operation goesout the loop and then terminates at step SP11.

By virtue of the generated information quantity controlling statedabove, the hierarchical coding which has little degradation of picturequality and high efficiency of compression can be performed.

(4) Other Embodiments of Fourth Embodiment

(4-1) In the abovementioned embodiment, such a case is described thatthe block activity valuelue P is determined based on the maximum valueof the difference value between the lower hierarchy data and the decodeddata obtained for each block with respect to the upper hierarchy data.However, the present invention is not to be limited to such an aspect,but the determination cancan be performed based on an average error, anabsolute value sum, a standard deviation, an n-th power sum, or afrequency of data which is larger than or equal to a threshold value ina block.

(4-2) In the abovementioned embodiment, such a case is described thatthe picture data is PCM coded at the coder. However, the presentinvention is not to be limited to such an aspect but other codingschemes, such as a quadrature coding scheme, can be applied.

(4-3) In the abovementioned embodiment, such a case is described thatthe plural combinations of the threshold value of the frequency tablewhich has been obtained for each hierarchy are previously stored in aROM, and then the combination of the threshold value by which thegenerated information quantity becomes nearest to the target value isobtained. However, the present invention is not to be limited to such anaspect but is possible to be adapted to set it independently for eachhierarchy.

(4-4) In the abovementioned embodiment, such a case is described thatthe lowermost hierarchy data is averaged for each 2 lines ×2 pixels at atime so that the picture data of the upper hierarchy is obtained,however, the present invention is not to be limited to such an aspectbut the average value can be obtained by other combinations.

(5) As stated above, according to the present invention, when thepicture data is sequentially recursively divided and coded into the dataof the plural hierarchies composed of different plural resolutions, theblock activity value is determined with respect to the predeterminedblock of the hierarchy data, and then the threshold value which is thedetermination standard of the division process to the lower hierarchydata is set from the frequency distribution of the block correspondingto the block activity value. Hereby the method for hierarchically codingthe picture data without lowering the efficiency of compression can beeasily realized.

6! Fifth Embodiment

(1) Picture Coding Apparatus of Fifth Embodiment

A picture coding apparatus 90 of the fifth embodiment has the sameschematic construction as a case of the third embodiment (FIG. 11) asshown in FIG. 36, and is composed of a hierarchical coding encoder unit90A which hierarchically codes an inputted picture data D31 and outputsit, and a generated information quantity control unit 90B which controlsthe generated information quantity in the hierarchical coding encoderunit 90A so that it attains the target value.

The hierarchical coding encoder unit 90A is composed of a data delayingmemory (not shown) and an encoder. The memory is provided in theinputting stage in order that the data can be delayed so that theencoding process will not be performed until an optimal control value isdetermined in the generated information quantity control unit 90B.

Meanwhile, the generated information quantity control unit 90B isadapted to be inputted an input picture data D31 and then determines athreshold value TH which is accommodated to the data to be processed,and also adapted to transmit the optimal control value, which isdetermined so that the inputted picture data D31 will be efficientlycoded in the hierarchical coding encoder unit 90A, to the encoder. Ithas a construction of a so-called feed-forward type buffering. By virtueof this construction, the accurate control of the generated informationquantity can be performed and a time delay generated by the feed-forwardtype buffering can be eliminated.

Hereupon, the selection of the division processing in the lowerhierarchy is performed, by a block activity value which is defined basedon the inter-hierarchy difference value. The upper hierarchy data iscomposed of four pixels of 2×2 of the lower hierarchy, and a block isdefined.

Denoting an upper hierarchy data by XO(i+1) and a lower hierarchy databy Xj(i), an inter-hierarchy difference coded value ΔXj(i) becomes equalto ΔXj(i)=XO(i+1)-Xj(i), where j=0 to 3. Meanwhile, denoting a blockactivity value determining function by G(·), a block activity value ACTis described as ACT =G(ΔXj(i)).

Further, denoting the case where the hierarchy determination flag FLG is0 by division stop, denoting the case where the hierarchy determinationflag FLG is 1 by division continue, method for confirming the divisiondetermination flag will be described. First, in the generatedinformation quantity control process, the activity ACT of all of thehierarchies is generated for each block, succeedingly, the determinationflag FLG is generated by the threshold value which corresponds to theactivity ACT of the all of the hierarchies. Further, a hierarchy inwhich the determination flag FLG is firstly to be 1 is searched in thesequence from the lowermost hierarchy for each block.

The hierarchical determination flag FLG of all of the upper hierarchyblocks than the hierarchy in which the determination flag FLG is firstlyto be 1, is set as "1". According to this manner, the determination flagFLG is updated. Further, the determination threshold value is changedbased on the control of generated information quantity, and an optimalthreshold value which satisfies the target value is selected. In thisconnection, in the case of this embodiment, the determination flag usedhere is different from a determination flag which is used in the codingprocess.

The block division selecting processing (i.e. the practical codingprocess) will be described below. When the determination flag FLG isdefined as FLG=0, the lower hierarchy is stopped the division, on thecontrary, when the determination flag FLG is defined as FLG=1, thedivision of the lower hierarchy is performed. The above processing iscomposed of two steps that the hierarchical determination flag FLG isdetermined previously for each block of each hierarchy by controllingthe generated information quantity, and the practical block divisionprocessing is performed based on the result.

(2) Hierarchical Coding Encoder Unit

The hierarchical coding encoder unit 90A has the construction shown inFIG. 37, and has the same construction as that is described with respectto FIGS. 12 and 13, excepting a point that coders 51 to 55 arestructured as shown in FIG. 38.

The coders 54, 53, 52 in this case output respectively threshold valuedetermined result information J1, J2, J3 which has been used torepresent division or non-division of the block to the coders 53, 52, 51of the lower hierarchy which are adjacent thereto. The coders 51, 52, 53output respectively the threshold value determined result informationJ4, J3, J2 to the coders 52, 53, 54 which are adjacent thereto.

That is, in the hierarchical coding encoder unit 90A, as to thehierarchy data, with respect to the block in which the divisionprocessing is stopped by the determination of the threshold value of theupper hierarchy, the processing returns to the hierarchy where thedivision processing is stopped when an useful activity is detected inthe following lower hierarchy, and resets the determination flag andperforms the determination of threshold value toward the lower hierarchyagain.

This is because the necessity of re-determination is recognized sincethe number of lower hierarchy data which corresponds to an upperhierarchy block increases on the hierarchical structure.

The coders 52 and 53 are structured as shown in FIG. 38 in practical.

The coder 53 inputs the difference data D43 to the coding circuit 53Aand the activity detecting circuit 53C of the division control unit 53B.The activity detecting circuit 53C detects an activity of each specifiedblock of the difference data D43, and gives thus obtained detectedresult to the following threshold value determining circuit 53D. Thethreshold value determining circuit 53D compares the detected result ofthe activity of each block with the threshold value data D57, andoutputs thus obtained determined result as the threshold valuedetermined result information J2 to the coding circuit 53A and the coder52 of the lower hierarchy which is adjacent to that. The coding circuit53A compression-codes and transmits as to the block having high activitybased on the threshold value determined result information J2, on thecontrary, does not transmit as to the block having low activity.

Here, the activity detecting circuit 53C and the threshold valuedetermining circuit 53D receive the threshold value determined resultinformation J1 which is outputted from the adjacent coder 54 of theupper hierarchy, so that the activity detection and the threshold valuedetermined result are performed in the case where the threshold valuedetermined result information J1 is that represents to perform divisionof the block. On the contrary, the activity detection and the thresholdvalue determination are not performed with respect to the correspondingblock in the case where the threshold value determined resultinformation J1 is that represents non-division of the block, and thethreshold value determined result information J2 which representsnon-division of the block is outputted from the threshold valuedetermining circuit 53D.

The coder 52 also performs the activity detection and the thresholdvalue determination with respect to the corresponding block, in the casewhere the activity detecting circuit 52C and the threshold valuedetermining circuit 52D receive the threshold value determined resultinformation J2 which represents division of the block from the adjacentcoder 53 of the upper hierarchy. On the contrary, the coder 52 does notperform activity detection and threshold value determination in the casewhere the threshold value determined result information J2 is thatrepresents non-division of the block, and outputs the threshold valuedetermined result information J3 which represents non-division of theblock from the threshold value determining circuit 52D.

As the above, in the hierarchical coding encoder unit 90A, ifnon-division determined result has been obtained once, the blockdivision is not performed (i.e., is not coded) with respect to thecorresponding block in the following lower hierarchies.

Further, in the hierarchical coding encoder unit 90A, when the thresholdvalue determined result information J4 which represents division of theblock can be obtained, the coder 52 receives this threshold valuedetermined result information J4 at the division control unit 52B toperform the determination of threshold value of the block activity, anddetermines whether or not to divide the block, even if the thresholdvalue determined result information J2 which represents non-division ofthe block is obtained for example, by the division control unit 53B ofthe coder 53.

(3) Generated Information Quantity Control Unit

FIG. 39 shows a block diagram of an example of the structure of thegenerated information quantity control unit.

First, at the averaging circuit 42, 1/4-averaging processing isperformed toward the picture data D31 which is same as that of theencoder unit of FIG. 37, to generate the second hierarchy data D32.

Secondly, at the averaging circuit 44, 1/4-averaging processing isperformed toward the second hierarchy data D32 to generate the thirdhierarchy data D33.

Similarly, the fourth hierarchy data D34 is generated by 1/4-averagingprocessing of the averaging circuit 46 toward the third hierarchy dataD33.

Lastly, the fifth hierarchy data D35 is generated by 1/4averagingprocessing at the averaging circuit 48.

Data frequency at the fifth hierarchy data D35 is registered into thefrequency table 73. This measures data frequency corresponding to thecompression processing which has been performed at the encoder unitdescribed above. For instance, in the case where compression processingby the PCM coding is performed for the fifth hierarchy data D35, adynamic range which is given with respect to each block is registered asa data, and in the case where the ADRC (adaptive dynamic range coding(U.S. Pat. No. 4,703,352)) is applied as the compression processingmethod, "DR" of the ADRC block is registered.

Succeedingly, the difference data D64 is generated from the fourthhierarchy data D34 and the fifth hierarchy data D35. As to thedifference data D64, the abovementioned detection of block activity isperformed at the activity detecting circuit 68. Thus detected blockactivity value D68 is registered into the frequency table 72.

The determination of block division in the upper hierarchy is determinedwith reference to the determined result of the block activity in all ofthe lower hierarchies.

Then, the frequency table 72 is defined by four variables, the firsthierarchy block activity value D65, the second hierarchy block activityvalue D66, the third hierarchy block activity value D67, and the fourthhierarchy block activity value D68.

The difference data D63 is generated from the third hierarchy data D32and the fourth hierarchy data D34. As to the difference data D63, itsblock activity value is detected at the activity detecting circuit 67.Thus detected activity value D67 is registered to the frequency table71.

Also in this case, the block division is determined with reference tothe determined result of the block activity value of all of the lowerhierarchies which are lower than the third hierarchy.

Therefore, the frequency table 71 of the third hierarchy is defined bythree variables, these are the first hierarchical block activity valueD65, the second hierarchical block activity value D66, and the thirdhierarchical block activity value D67.

The difference data D62 is generated from the second hierarchy data D33and the third hierarchy data D32, and the block activity value D66 isoutputted from the activity detecting circuit 66. The detected blockactivity value D66 is registered to the frequency table 70.

In this case, the block division is determined with reference to thedetermined result of the block activity of the first hierarchy.

The frequency table 70 of the second hierarchy is defined by twovariables, the first hierarchy block activity value D65 and the secondhierarchy block activity value D66.

Lastly, the difference data D61 is generated from the first hierarchydata D31 and the second hierarchy data D32, and the block activity valueD65 is outputted from the activity detecting circuit 65. The detectedblock activity value D65 is registered to the frequency table 69.

With respect to the first hierarchy, the determination of thresholdvalue of the block activity is independently performed and the result isperformed, therefore it is not needed to monitor the block activity ofthe upper hierarchy. That is, the frequency table 1 of the firsthierarchy is to be one-dimensional frequency table which is composed ofthe first hierarchy block activity data D65.

In generating process of the frequency table, three pixels which areobjects to be transmitted by the encoder practically, are used out offour pixels of a lower hierarchy corresponding to one pixel of the upperhierarchy, to grasp correctly the quantity of data to be transmitted ofthe encoder unit.

The control of generated information quantity is performed using thusgenerated frequency tables 69 to 73. Each frequency table and thecontrol unit of the latter stage are connected each other withbi-directional signal channels D69 to D73.

In the control unit, a threshold value for each frequency table istransmitted to each frequency table.

In each frequency table, the generated information quantitycorresponding to the to the threshold value is detected.

The generated information quantity in each frequency table istransmitted via the signal channels D69 to D73 to the control unit 74.

In the control unit 74, the total generated information quantity to becontrolled is calculated by integrating the received generatedinformation quantity in each frequency table.

This total generated information quantity is compared with the targetvalue, and the threshold value is changed according to the comparisonresult so that the target value is satisfied.

The threshold value updated again is transmitted from the control unit74 via the signal channel D69 to D73 to each frequency table.

The generated information quantity corresponding to the above thresholdvalue is transmitted to the control unit 74 again.

The control result D57 for attaining the target value is determinedfinally by repeating the above processing.

The detected generated information quantity control value D57 istransmitted to the hierarchical coding encoder unit as shown by theblock diagram of FIG. 36.

The data to be controlled is to be waited into a memory M1 which isincluded in the encoder unit, while this generated information quantitycontrol unit is processing.

In the above control of information quantity, the threshold valueapplied to the object data can be determined, thereby a coding can berealized with high efficiency.

FIGS. 40(A) to 40(E) show respectively frequency tables of the blockactivities which has been obtained with respect to the uppermosthierarchy data to the lowermost hierarchy data. Here, as to thefrequency table of the fifth hierarchy shown in FIG. 40(A), since thedifference data is not an object data, the frequency table by dynamicrange is generated. For instance, in the case where the compressionprocessing by the PCM coding is performed on the fifth hierarchy dataD35, the dynamic range which is given with respect to each block isregistered as a data, on the other hand, in the case where the ADRC(adaptive dynamic range coding (U.S. Pat. No. 4,703,352)) is applied asa compression processing method, the DR of the ADRC block is registered.

An example of the frequency table for control of the generatedinformation quantity in case of having fifth hierarchies is shown inFIGS. 41 to 47.

First, a defining equation is introduced that calculates the totalgenerated information quantity.

To calculate the generated information quantity, it is needed to countthe number of activity blocks which is larger than or equal to thedivision determination threshold value in each hierarchy. However, inthe control of the generated information quantity in the hierarchicalcoding by determination flag confirming method, the divisiondetermination of object block must be performed considering thedetermined result of division of all of the lower hierarchies for eachblock in the upper hierarchy.

At this time, as to the block activity determination threshold valueused to the determination of division in each hierarchy, the firsthierarchy division determination threshold value is denoted by TH1, thesecond hierarchy division determination threshold value is denoted byTH2, the third hierarchy division determination threshold value isdenoted by TH3, and the fourth hierarchy division determinationthreshold value is denoted by TH4.

The division of the lower hierarchy of the block which is larger than orequal to the threshold value is performed, in all of hierarchies. In theupper hierarchy, the division of block is stopped in the case wherethere is no block activity which is larger than or equal to thethreshold value in all of the lower hierarchies and when the blockactivity of the hierarchy is less than the threshold value.

FIG. 41(A) shows a frequency table of the fifth hierarchy which is theuppermost hierarchy.

As to the frequency table of the fifth hierarchy, the control ofinformation quantity corresponding to the coding processing is performedbecause the object data is not difference data.

In the case where the fixed-length coding such as the linearquantization is applied, it is not needed to produce a frequency table.On the control of generated information quantity, it may use thefollowing calculation of generated information quantity.

That is, assuming that the sum of pixel numbers in the block to bedivided in the first hierarchy as "M1", the number of quantization bitsof the first hierarchy data as "Q1", the number of determination flagbits of the first hierarchy as "N1", then the generated informationquantity "I1" in the first hierarchy is given by the following equation:

    I1=4·Q1·M1·(3/4)+N1             (18)

In the first term of Equation (18), each number of bits is quadrupled,because in the case of this example, each block is divided into 2lines×2 pixels. Further, in the first term, it is multiplied by 3/4,because the characteristic is reflected that, on a structure that anupper hierarchy value is generated based on the mean value of lowerhierarchy values, the fourth non-transmission pixel value of lowerhierarchy can be restored by means of an arithmetic equation using theupper hierarchy value and three pixels of the lower hierarchy value.

By the way, in the second term, N1 is added to the number of blocks inthe first hierarchy, it means that the respective blocks are transmittedwith adding one bit as a division determination flag.

Similarly, as to the second, the third, and the fourth hierarchies,assuming that the sum of pixel numbers in the block to be divided ineach hierarchy as M2, M3, M4, the number of quantization bits in eachhierarchy as Q2, Q3, Q4, the number of determination flag bits in eachhierarchy as N2, N3, N4, then the generated information quantity Ik(k=2, 3, 4) in each hierarchy is given by the following equation:

    I=I1+I2+I3+I4+I5                                           (19)

Using the generated information quantities I1 to I4 of the first to thefourth hierarchy and the generated information quantity I5 of the fifthhierarchy, the total generated information quantity I which is generatedby the coding processing of the hierarchical coding encoder unit 40A canbe obtained as a sum of generated information quantities for eachhierarchy as the following equation:

    Ik=4·Qk·Mk·(3/4)+Nk             (20)

Here, the number of bits of the determination flag is added to thegenerated information quantity of each hierarchy. However, theinformation quantity of this flag is equal to the number of blocks whichhas been performed the division processing in the upper hierarchy. Thespatial position of each block can be specified in each hierarchy by ahistory of the determination flag from the upper hierarchy.

Now, the individual frequency tables will be explained.

As stated above, since the frequency table of the uppermost hierarchydata depends on the compression scheme, it is not determined uniquely.However, the generated information quantity can be controlled usingmeans such as a frequency table.

Next, as to the first hierarchy data, the block frequency toward theblock activity value ACT1 is registered. By applying the first hierarchyfrequency table of FIG. 41, the generated information quantity which isrelated to the threshold value TH1 can be easily calculated.

Since the blocks which are larger than or equal to the threshold valueTH1 are the object of division, the generated information quantity onthe fourth hierarchy is calculated by computing the sum of the number ofblocks which are not less than the threshold value.

Next, an example of the frequency table of the second hierarchy is shownin FIG. 42.

In the determination flag confirming scheme, the number of blocks whichis over the threshold value TH2 in the second hierarchy is counted, forthe block which received the determination of block division stop in thefirst hierarchy.

Then, such a frequency table is introduced that is defined by twovariables, that are the first hierarchy block activity value ACT1 andthe second hierarchy block activity value ACT2.

In other words, such a block frequency is obtained that is larger thanor equal to the threshold value TH1 of the first hierarchy and largerthan or equal to the threshold value TH2 of the second hierarchy.

As to this operation, by calculating the block frequency which is largerthan or equal to the threshold value TH1 at the ACT1 axis and largerthan or equal to the threshold value TH2 at the ACT2 axis on thefrequency table of FIG. 42, the generated information quantity in thesecond hierarchy which satisfies the above conditions can be calculated.

FIG. 42 shows the state where the block activity values ACT2 of thesecond hierarchy are distributed for each value of the ACT1 in the casewhere the ACT1 is measured discretely.

Next, the examples of the frequency tables for the third hierarchy andthe fourth hierarchy are shown in FIG. 43.

In accordance with the same idea as that of the frequency table of thesecond hierarchy, a frequency table which is defined by severalvariables is produced.

In the third hierarchy, the blocks which are defined by the respectiveblock activities ACT1, ACT2, and ACT3 of the first hierarchy, the secondhierarchy, and the third hierarchy, are registered to the frequencytable. This situation is shown in FIG. 43(A).

In the third hierarchy, by calculating the block frequency which islarger than or equal to the threshold value TH1 at the ACT1 axis, largerthan or equal to the threshold value TH2 at the ACT2 axis, and largerthan or equal to the threshold value TH3 at the ACT3 axis, the generatedinformation quantity in the third hierarchy is calculated.

In the fourth hierarchy, the blocks which are defined by the respectiveblock activities ACT1, ACT2, ACT3, and ACT4 of the first hierarchy, thesecond hierarchy, the third hierarchy, and the fourth hierarchy areregistered to the frequency table. This situation is shown in FIG.43(B).

In the case of the fourth hierarchy, by calculating the block frequencywhich is larger than or equal to the threshold value TH1 at the ACT1axis, larger than or equal to the threshold value TH2 at the ACT2 axis,larger than or equal to the threshold value TH3 at the ACT3 axis, andlarger than or equal to the threshold value TH4 at the ACT4 axis, thegenerated information quantity in the fourth hierarchy is calculated.

The generated information quantity toward the threshold value can becalculated utilizing the abovementioned five kinds of frequency tables,and can be controlled so as to coincide with the t ar get informationquantity.

As to the threshold value of each hierarchy which is utilized to controlthe generated information quantity, there are methods for changing itindependently for each hierarchy.

For instance, there is such a scheme that the target informationquantity is previously set for each hierarchy and then the thresholdvalue is independently changed for each hierarchy, so that it iscontrolled so as to coincide with the target information quantity.

Also, as another scheme, such a scheme that the combinations of thethreshold values for each hierarchy are previously prepared, and thenthese threshold value sets are applied in accordance with a controlsequence is also considerable, and hereby the control is simplified.

A frequency table will be described below.

In the abovementioned scheme for controlling the generated informationquantity which utilizes the frequency table of each hierarchy, in eachhierarchy, the block frequency whose block activity value at eachhierarchy is larger than or equal to the threshold value, is calculatedconsidering the division determined result of the upper hierarchy, sothat the optimal control value is detected.

In order to shorten the time for calculating the block frequency whichis larger than or equal to the threshold value, the frequency table inwhich the block frequency is registered may be reconstructed into anintegration type frequency table.

An example of this integrating frequency table is shown in FIG. 45.

It is supposed that a block activity value has been registered with theresult that an example of a frequency table which is shown in FIG. 44has been obtained. In this case, to simplify the explanation, an exampleof which the block activity value is one variable is shown.

The integrating frequency table (FIG. 45) has such a structure that theintegrating calculation is performed starting with the block frequencywhich corresponds to the maximum value of the block activity value ofthe frequency table of FIG. 44, and toward the block frequency whichcorresponds to the smaller block activity value, so that the respectiveresults of the integration are re-registered in the frequency table.

This process is represented by the following equation: ##EQU5## Here,SUM(·) represents an integrated block frequency, "N(·)" represents ablock frequency in a frequency table, "act" denotes a block activityvalue variable in the integrating frequency table, "ACT" denotes a blockactivity value variable in the frequency table, and "n" denotes themaximum value of a variable in the frequency table.

What is meant by Equation (21) is such a process that a block frequencyof a block activity value address is read and added to the integratedvalue which has been obtained up to the upper block activity value, andthen the result is written into the present block activity valueaddress.

This result is shown in FIG. 45. In this integrating frequency table,the sum of the block frequency of the hatched portion of FIG. 44corresponds to the threshold value TH coordinate data I.

By virtue of this integrating frequency table, it becomes unnecessary tocalculate the sum of the block frequency of the hatched portion of FIG.44 each time the threshold value TH is changed.

That is to say, by outputting the integrated block frequency whichcorresponds to the threshold value of the integrating frequency table,the calculation of the sum of the block frequency is realized.

FIG. 45 also shows an example of one variable, which can be applied tothe first hierarchy frequency table of FIG. 41.

The second hierarchy frequency table of FIG. 42 shows the case of twovariables. By expanding Equation (21), an integrating frequency table isproduced and represented by the following equation: ##EQU6## Here,"SUM(·)" represents an integrated block frequency, "N(·)" represents ablock frequency in a frequency table, "act1" denotes the first hierarchycorresponding variable in an integrating frequency table, "act2" denotesthe second hierarchy corresponding variable in the integrating frequencytable, "ACT1" denotes the first hierarchy variable in the frequencytable, "ACT2" denotes the second hierarchy variable in the frequencytable, and "n" denotes the maximum value of a variable in the frequencytable.

In an integrating frequency table which is produced in accordance withEquation (22), an integrated block frequency, which corresponds to theaddress of the determination threshold value TH1 of the first hierarchyand the determination threshold value TH2 of the second hierarchy,indicates the sum of the block frequency which is larger than or equalto the threshold value TH1 and also larger than or equal to thedetermination threshold value TH2.

In this way the generated information quantity at the second hierarchycan be calculated.

With respect to the frequency tables of the third hierarchy and thefourth hierarchy shown in FIG. 43, the time for calculating the blockfrequency sum can also be shortened by utilizing an integratingfrequency table.

In these cases the number of block activity variables increases,therefore the number of integration increases.

First, the operational expression in the case of the third hierarchy isrepresented by the following equation: ##EQU7## Here, "SUM(·)"represents an integrated block frequency, "N(·)" represents a blockfrequency in a frequency table, "act1" denotes the first hierarchycorresponding variable in an integrating frequency table, "act2" denotesthe second hierarchy corresponding variable in the integrating frequencytable, "act3" denotes the third hierarchy corresponding variable in theintegrating frequency table, "ACT1" denotes the first hierarchy variablein the frequency table, "ACT2" denotes the second hierarchy variable inthe frequency table, "ACT3" denotes the third hierarchy variable in thefrequency table, and "n" denotes the maximum value of a variable in thefrequency table.

In the integrating frequency table which is produced in accordance withEquation (23), the integrated block frequency, which corresponds to theaddress of the determination threshold value TH1 of the first hierarchy,the determination threshold value TH2 of the second hierarchy, and thedetermination threshold value TH3 of the third hierarchy, indicates thesum of the block frequency which is larger than or equal to thethreshold value TH1 and also larger than or equal to the threshold valueTH2 and also larger than or equal to the determination threshold valueTH3.

In this manner, the generated information quantity in the thirdhierarchy can be calculated.

Further, a process which is related to the frequency table of the fourthhierarchy shown in FIG. 43 will be described.

In this case, there are four kinds of block activity value variables,therefore the number of integrating calculations becomes the most.

The operational expression in the case of the fourth hierarchy isrepresented by the following equation: ##EQU8## Here, "SUM(·)"represents an integrated block frequency, "N(·)" represents a blockfrequency in a frequency table, "act1" denotes the first hierarchycorresponding variable in an integrating frequency table, "act2" denotesthe second hierarchy corresponding variable in the integrating frequencytable, "act3" denotes the third hierarchy corresponding variable in theintegrating frequency table, "act4" denotes the fourth hierarchycorresponding variable in the integrating frequency table, "ACT1"denotes the first hierarchy variable in the frequency table, "ACT2"denotes the second hierarchy variable in the frequency table, "ACT3"denotes the third hierarchy variable in the frequency table, "ACT4"denotes the fourth hierarchy variable in the frequency table, and "n"denotes the maximum value of a variable in the frequency table.

In the integrating frequency table which is produced in accordance withEquation (24), the integrated block frequency, which corresponds to theaddress of the determination threshold value TH1 of the first hierarchy,the determination threshold value TH2 of the second hierarchy, thedetermination threshold value TH3 of the third hierarchy, and thedetermination threshold value TH4 of the fourth hierarchy, indicates thesum of the block frequency which is larger than or equal to thethreshold value TH1, also larger than or equal to the threshold valueTH2, also larger than or equal to the threshold value TH3, also largerthan or equal to the threshold value TH4.

In this manner, the generated information quantity at the fourthhierarchy can also be calculated.

As a result of this process, the calculation of the generatedinformation quantity based on the number of the dividing object blocksin each hierarchy based on Equation (19) is realized.

By the introduction of the above described integrating frequency table,the time for controlling the generated information quantity can beshortened significantly.

Such a method will be described below that the time for controlling thegenerated information quantity is further shortened on this integratingfrequency table.

The integrating frequency table which is used in this proposal isutilized to calculate the information quantity which is generated towardthe division determination threshold value.

In the actual threshold value processing, a large determinationthreshold value can not be practically used, from the viewpoint of thedegradation of the picture quality. Hence, it is proposed herein to makefrequency tables whose block activity value is clipped. Such a situationis shown in FIGS. 46 and 47.

As shown in FIG. 46, on the condition that the block activity value isclipped at LMT, the block frequency which are larger than or equal toLMT are all registered as LMT to the frequency table.

As a result, the block frequency at LMT become large as indicated in thefigure. The block frequency sum to be calculated is the hatched portion.

The integrating frequency table toward this frequency table is shown inFIG. 47. The integrating calculations which are shown in Equations (21)to (24) are performed with respect to the interval, which extends fromthe block activity value LMT instead of the maximum value "n" of theblock activity value, to "0".

The block frequency sum to be calculated is the integrated blockfrequency I of the coordinate of the threshold value TH. As shown inthis example, the same result as that of FIG. 45 is obtained. By theintroduction of clipping into the block activity value of the frequencytable, a shortening of the integrating frequency table generating timeand a miniaturization of the frequency table memory space can berealized.

As the frames to which this scheme is applied, two frames can beconsidered. One of these is the case where clipping value LMT is changedfor each hierarchy, and the other is the case where clipping value LMTis fixed for all hierarchies.

The former is utilized when there are clear differences in thedistribution of the inter-hierarchy difference values of each hierarchy,and the latter is utilized when there are little differences in thedistribution of the inter-hierarchy difference values of each hierarchy.

Note that, FIG. 48 shows a flowchart of the hierarchical coding process.In the step SP2, "4" is registered in the hierarchy counter I forstoring the hierarchy number, so that the frame of this hierarchizationis determined.

Further, at step SP3, the hierarchical data is produced by the generatedinformation quantity calculation, and at step SP4, each block activityvalue is detected. With respect to this activity value, at step SP5, themulti-dimensional frequency table which is abovementioned in relation toFIG. 42 is generated and registered, hereby the generated informationquantity controlling is performed and the optimal control value isdetermined.

Further, at step SP6, the hierarchical coding is performed at theencoder side based on this control value. At first, the coding and thedecoding are performed with respect to the data of the fifth hierarchywhich is the uppermost hierarchy. The result of this process becomes tothe initial value of the process at the lower hierarchy, and theinter-hierarchy difference value between this result and the lowerhierarchy is produced at step SP7. Further, at step SP8, based on thegenerated information quantity control value which is determined at theupper stage, the division selecting and the coding at the lowerhierarchy are performed.

After the processing of each hierarchy, the hierarchy counter I isdecremented at step SP9. And then, at step SP10, a terminationdetermination is performed with respect to the content of the hierarchycounter I. In the case where it is not to be terminated, the process ofthe lower hierarchy is further continued. In the case where theprocesses of all hierarchies have been terminated, the operation goesout the loop and then terminates at step SP11.

By virtue of the generated information quantity controlling statedabove, the hierarchical coding which has little degradation of picturequality and high efficiency of compression can be performed.

(4) Other Embodiments of Fourth Embodiment

(4-1) In the abovementioned embodiment, such a case is described thatthe block activity value P is determined based on the maximum value ofthe difference value between the lower hierarchy data and the decodeddata obtained for each block with respect to the upper hierarchy data.However, the present invention is not only limited to this, but thedetermination can be performed based on an average error, an absolutevalue sum, a standard deviation, an n-th power sum, or a frequency ofdata which is larger than or equal to a threshold value in a block.

(4-2) In the abovementioned embodiment, such a case is described thatthe picture data is PCM coded at the coder. However, the presentinvention is not only limited to this, but other coding schemes, such asa quadrature coding scheme, can be applied.

(4-3) In the abovementioned embodiment, such a case is described thatthe plural combinations of the threshold value of the frequency tablewhich has been obtained for each hierarchy are previously stored in aROM, and then the combination of the threshold value by which thegenerated information quantity becomes nearest to the target value isobtained. However, the present invention is not only limited to this,but can be adapted to set it independently for each hierarchy.

(4-4) In the abovementioned embodiment, such a case is described thatthe lowermost hierarchy data is averaged for each 2 lines×2 pixels at atime so that the picture data of the upper hierarchy is obtained,however, the present invention is not only limited to this, but theaverage value can be obtained by other combinations.

(5) As stated above, according to the present invention, when thepicture data is sequentially and recursively divided and coded into thedata of the plural hierarchies composed of different plural resolutions,the block activity value is determined with respect to the predeterminedblock of the hierarchy data, and then the threshold value which is thedetermination standard of the division process to the lower hierarchydata is set from the frequency distribution of the block correspondingto the block activity value. Thereby, the method for hierarchicallycoding the picture data without the lowering of the efficiency ofcompression can be easily realized. 7! Sixth Embodiment

(1) Picture Coding Apparatus of Sixth Embodiment

The picture coding apparatus 100 of the sixth embodiment has the sameschematic construction as the case of the third embodiment (FIG. 11) asshown in FIG. 49, and is composed of a hierarchical coding encoder unit100A which hierarchically codes an inputted picture data D31 and outputsit, and a control unit 100B which controls the generated informationquantity in the hierarchical coding encoder unit 100A so that it attainsthe target value.

The hierarchical coding encoder unit 100A is composed of a memory M1 fordelaying data (FIG. 50) and an encoder. The memory M1 is provided in theinputting stage in order that the data can be delayed so that theencoding process will not be performed until an optimal control value isdetermined in the generated information quantity control unit 100B.

Meanwhile, the generated information quantity control unit 100B isadapted to be inputted the input picture data D31 and then sets anoptimal control value S1 which is accommodated to the data to beprocessed, and also adapted to transmit this to the hierarchical codingencoder 40A, so that the coding can be efficiently performed in thehierarchical coding encoder unit 40A. It has a construction of aso-called feed-forward type buffering.

(2) Hierarchical Coding Encoder Unit

The hierarchical coding encoder unit 100A has the construction shown inFIG. 50, and has the same construction as that is described with respectto FIGS. 12 and 13, excepting the points that the compressed picturedata of five hierarchies having different resolutions is generated andthe input picture data D31 is inputted via the memory M1, and the coders51 to 55 are structured as shown in FIG. 51.

The coders 51 to 55 of this case perform block division determination byutilizing the relation of signals existing in the same space. That is,in FIG. 51, the coder 54 inputs the difference data D44 to the codingcircuit 54A, and at the same time inputs to the color signal detectingsignal 54B and the luminance signal detecting circuit 54E. The luminancesignal detecting circuit 54E extracts a luminance component which isincluded in the difference data D44, and detects an activity of theextracted luminance component for each block. The threshold valuedetermining circuit 54G compares the detected luminance signal activitywith a predetermined threshold value, and gives thus obtained determinedresult of the threshold value to the following threshold value settingcircuit 54H. In the threshold value setting circuit 54H, when thedetermined result in the threshold value determining circuit 54G is thatrepresents the luminance signal activity is larger than thepredetermined threshold value, the threshold value is set comparativelylow, and when said determined result is that represents the luminancesignal activity is smaller than the predetermined threshold value, thethreshold value is set comparatively high. At this time, the thresholdvalue setting circuit 54H determines the size of the threshold valuecorresponding to the optimal control value S1. Thus set threshold valueis given to the threshold value determining circuit 54D.

Besides, in the coder 54, an activity of each block of the color signalcomponent which is extracted by the color signal detecting circuit 54Bis detected by the activity detecting circuit 54C, and thus obtainedcolor signal activity is given to the threshold value determiningcircuit 54D.

The threshold value determining circuit 54D determines the color signalactivity by the threshold value set by the threshold value settingcircuit 54H, and controls block division at the coding circuit 54Aaccording to the determined result. That is to say, when the colorsignal activity is larger than or equal to the set threshold value, theblock division is performed, on the contrary, when the color signalactivity is less than the threshold value, the block division is notperformed.

In this manner, in the coder 54 (the coders 51 to 53 are similar tothat), the threshold value is temporary set based on the activity of theluminance signal, in order to determine the activity of the color signalusing the set threshold value, and the division of block is controlledbased on the determined result.

Here, defining an area of lower hierarchy data which corresponds toupper hierarchy data a s "block", activity is represented by acorrelation value, such as a maximum value, a mean value, an absolutevalue sum, a standard deviation, or an n-th power sum of theinter-hierarchy difference data D41 to D44 in a predetermined block.That is, when an activity is low, it can say that this block is a planeblock.

At this time, when the block activity is higher than the predeterminedthreshold value, the coders 51 to 54 determine this block as a divisionblock, and code and transmit the data of the block with adding adivision determination flag that represents this block is division blockthereto.

On the contrary, when the block activity is less than the predeterminedthreshold value, the coders 51 to 54 determine this block as anon-division this block, to not transmit the data of this block, thentransmit a non-division determination flag that represents this block isnon-division block. This non-division block is replaced to an upperhierarchy data at the side of decoding device.

(3) Division Processing

In the hierarchical coding method of this embodiment, a method is usedthat a determination flag is not reflected to determination in thefollowing lower hierarchy (hereinafter this is called independentdetermining method). That is, in the independent determining method, adivision selecting processing based on the determination of thresholdvalue every time is performed independently for each hierarchy. Forinstance, as to the block that receives non-division determination once,in the following lower hierarchy, the determination of activity isperformed again to select division or non-division again. Thereby, inthe hierarchical coding method applied the independent determiningmethod, in an upper hierarchy, there is no effects of the determinationflag of a lower hierarchy, therefore, the hierarchical coding withlittle deterioration of picture quality can be realized.

In addition to the above structure, in the hierarchical coding encoderunit 100A, division determination of the color signal is not performedindependently but it is performed considering the luminance signal inthe same space which has a correlation to the color signal to eachother.

In the hierarchical coding encoder 100A, a threshold value which is usedto the block division determination of the color signal is changed inaccordance with the block activity of the luminance signal.

More specifically, in the hierarchical coding encoder unit 100A, when adata value of the color signal upper hierarchy data is denoted byX_(i+1) (0), a data value of the color signal lower hierarchy data isdenoted by X_(i) (j) j=0 to 3!, the color signal inter-hierarchydifference coded value is denoted by ΔX_(i) (j) =X_(i+1) (0)-X_(i) (j)j=0 to 3!, the color signal block activity determination function isdenoted by G(·), the color signal block activity is denoted by ACT_(C)=G(ΔX_(i) (j)) j=0 to 3!, and the luminance signal block activity in thesame space is denoted by ACT_(Y), then when the luminance signal blockactivity ACT_(Y) is larger than or equal to the predetermined thresholdvalue TH0, the division determination threshold value TH of the colorsignal is set to TH0_(C). When the luminance signal block activityACT_(y) is less than the threshold value TH0, the division determinationthreshold value TH of the color signal is set to TH1_(C) (>TH0_(C)).

In the hierarchical coding encoder 100A, when the color signal blockactivity value ACT_(C) is larger than or equal to the threshold valueTH, the division in the lower hierarchy is performed, on the contrary,when the color signal block activity value ACT_(C) is less than thethreshold value TH, the division in the lower hierarchy is stopped.

Here, for instance, in the case where the luminance signal blockactivity value ACT_(Y) is larger than or equal to the threshold valueTH0, this represents that the case where the fluctuation of theluminance signal is large such as the edge of an object. In such a case,the hierarchical coding encoder 100A applies the division determinationthreshold value TH0_(C) which is comparative small as the divisiondetermination threshold value TH of the color signal, in order tocontrol so that the division is performed same as the luminance signal.

On the contrary, when the luminance signal block activity value ACT_(Y)is less than the threshold value TH0, this represents that thefluctuations of the luminance signal is not large, in such a case, thehierarchical coding encoder 100A applies the division determinationthreshold value TH1_(C) which is larger than the division determinationthreshold value TH0_(C) as the division determination threshold value THof the color signal, in order to improve the compression efficiency.

Here, FIG. 53 shows a comparison of signal waveform between the casewhere the division of the color signal is controlled by changing thethreshold value TH according to the luminance signal block activityvalue ACT_(Y) as this embodiment, and the case where the division of thecolor signal is controlled by determining the block activity value undera constant threshold value.

FIG. 53 shows a waveform of one-dimensional signal for explanation,assuming a color picture as object to be coded. In this example, asshown in FIGS. 53(A) and 53(B), it shows the case of coding the signalwhose luminance signal fluctuates remarkably such as that of the edge ofobject and whose fluctuation of the color signal is comparativelysmaller than that of the luminance signal.

FIG. 53(C) shows the divided result of a color signal in the case wherethe division is controlled by determining the block activity for thecolor picture signal as the above under a constant threshold value. FIG.53(C) represents that the non-division processing is selected in all ofthe blocks of the color signal.

It is obvious from FIG. 53(C), in the case where the division of colorsignal is controlled by determining the block activity under a constantthreshold value, when a fluctuation of color signal is smallcomparatively, the non-division processing may be selected even in thatof the edge of object, due to difference of the division determinedresult between luminance signal and color signal. As a result, an upperhierarchy data is utilized as a restored value of the non-division blockdata. Thereby, the signal waveform is to be step-like. It is not anoticeable step-like waveform in general, however, this step-likewaveform is recognized at a plane portion neighboring to the positionwhere the luminance signal fluctuates remarkably as deterioration ofpicture quality of the color signal.

More particularly, in the case where the block size of the luminancesignal differs from that of the color signal, the difference of thepicture quality is remarkable owing to the difference of the processingbetween the luminance signal and the color signal existing in the samespace. In such a manner, the deterioration of picture quality based onthe color signal occurs.

On the contrary, in the case where the division is controlled bychanging the threshold value TH according to the luminance signal blockactivity value ACT_(Y), division of the color signal in the block wherethe fluctuation of the luminance signal is large such as that of aportion of the edge of object.

Consequently, the division determined result of the luminance signal andthat of the color signal coincide with each other, and thereforedeterioration of the picture quality at the edge portion of objectcaused by a step-like waveform can be avoided.

That is, in the case where this hierarchical coding is utilized for thepicture which is composed of plural signals as color picture, thedivision determination is performed considering a relation betweensignals existing in the same space, without performing the divisiondetermination of each block independently with respect to respectivesignals, thereby the picture quality can be improved.

In the above manner, in the hierarchical coding apparatus 100, thecompression efficiency can be improved and deterioration of the picturequality can be reduced.

In this connection, FIG. 54 shows a flowchart of the hierarchical codingprocess by the hierarchical coding apparatus. At step SP2, "4" isregistered into the hierarchy counter I for storing the hierarchynumber, so that the frame of this hierarchical coding is determined.

Further, at step SP3, the hierarchical data is generated by performingthe generated information quantity calculation at the generatedinformation quantity control unit 100B, and at the following step SP4,each block activity value is detected. At step SP5, the generatedinformation quantity control unit 100B determines the optimal controlvalue S1 based on this activity value.

Further, at step SP6, the hierarchical coding is performed by thehierarchical coding encoder unit 100A based on the optimal control valueS1. That is, coding and decoding are performed for the fifth hierarchydata being the uppermost hierarchy first. This result is set to theinitial value of the process in the lower hierarchy, and theinter-hierarchy difference value between this result and the lowerhierarchy is produced at step SP7. Further, at step SP8, divisionselecting and coding in the lower hierarchy are performed based on theoptimal control value S1 which is determined at the step SP5.

After processed the respective hierarchies, the hierarchy counter I isdecremented at step SP9. Then, at step SP10, a termination determinationis performed for the contents of the hierarchy counter I. In case ofterminated the process of all of the hierarchies, the operation goes outthe loop and terminates the above hierarchical coding processing at stepSP11.

(4) Effects of the Embodiment

According to the above structure, when block division is performed fromthe upper hierarchy to the lower hierarchy, the division determinationis performed considering a relation between signals existing in the samespace, thereby the picture coding method in which compression can beperformed efficiently and the deterioration of the picture quality canbe reduced, can be realized.

(5) Other Embodiments

(5-1) In the aforementioned embodiment, such a case is described thatluminance signal and color signal are utilized as signals which form apicture and have a correlation to each other, and the division thresholdvalue of the color signal is changed based on the block activity valueof the luminance signal. However, the present invention is not onlylimited to this, but for instance, the three primary colors signals ofRGB are used as signal that has a relation to each other and forms acolor picture, so that the division threshold value of the anothersignals can be changed based on the signal characteristic of one ofthese. In short, the division threshold value can be selected based onthe relation of signals which have a relation to each other.

(5-2) In the aforementioned embodiments, such a case is described thatthe picture coding method according to the present invention is appliedto the independent determining method for determining threshold valueindependently to each hierarchy every time and performing the divisionprocessing. The present invention is not only limited to this, the sameeffect as the aforementioned embodiments can be obtained, also in thecase of applying to the determining method that when the division of thelower hierarchy is temporarily stopped by the division determination inthe upper hierarchy, the division of the following lower hierarchy isstopped, further in the case of applying to the determining method thatwhen the determined result representing that the block activity value issmaller than the predetermined threshold value is obtained, the divisionstop flag for stopping the way of division of a plurality of lowerblocks corresponding to this block is temporarily generated, and whenthe determined result representing that the block activity of at leastone of a plurality of blocks is larger than or equal to thepredetermined threshold value is obtained, the division stop flag ischanged to the division continue flag.

Further, the present invention is not only limited to the above, but iswidely applicable to the case where, in the hierarchical coding method,a plurality of blocks having different resolutions are existed inhierarchy data.

(6) As described above, according to the present invention, in a picturecoding apparatus in which a picture data is sequentially and recursivelydivided into plural hierarchy data having different resolutions fromeach other and coded, the block activity value with respect to thepredetermined block of the hierarchy data excepting the uppermosthierarchy data having a lowest resolution is determined, and when theblock activity value is less than the predetermined threshold value, theblock division of the lower hierarchy data corresponding to the blockwhose block activity is determined is stopped and the division stop flagis transmitted as a determination flag: the threshold value is selectedbased on the first signal out of a plurality of signals which have arelation to each other and form a picture; the above threshold value iscompared to the block activity value of the second signal out of thesignals having the relation so as to determine an activity of the secondsignal; and the block division is controlled based on the determinedresult, thereby when the picture data is hierarchical coded, thecompression efficiency can be improved and the deterioration of thepicture quality can be reduced.

8! Seventh Embodiment

(1) Picture Coding Apparatus of Seventh Embodiment

The picture coding apparatus 110A of the seventh embodiment re-forms thehierarchical coded data D51 to D55, which are obtained from thehierarchical coding encoder unit 110A, to transmission blocks at thetransmission block forming unit 111, and outputs it as the transmissiondata D_(OUT), as shown in FIG. 55, in addition to the structure of thefourth embodiment which is described accompanying with FIGS. 11 to 18.

(2) Data Structure of Transmitting Block

Here, the data which is generated by the generated information quantitycontrol method as described above at the hierarchical coding encoderunit 110A, can be classified into the fixed-length data such as theuppermost hierarchy coded data D55 which is outputted from the coder 55(FIG. 55), and the variable-length data of the first to the fourthhierarchy difference value coded data D51 to D54 which are outputtedfrom the coders 51 to 54.

Therefore, in the hierarchical coding encoder unit 110A, as shown inFIG. 56, the fixed-length data block 120 is formed by collecting eachfixed-length data into groups for each frame forming a picture, and thevariable-length data block 121 is formed by collecting eachvariable-length data of the above frame into groups. Thisvariable-length data block 121 is arranged after the fixed-length datablock 120 in order to form the unit block 122 for transmission(hereinafter this is called transmission block 122). The transmissionblock 122 is sequentially outputted to the transmission line.

In practice, in the transmission block 122, the transmission blockidentification code C1 which is composed of the SYNC code designatingthe head position of the block 122, the information code showing thecontents of the picture data, and the like (hereinafter, referred to asidentification information code), is arranged at the head of thefixed-length data block 120 (that is the head of the transmission block122).

Further, in the transmission block 122, the uppermost hierarchy codeddata D55 is arranged immediately after the transmission blockidentification code C1, thereby when searching for the desired pictureusing the identification code, the picture can be sequentially restoredat high speed by using the uppermost hierarchy coded data D55 which hasless information quantity. Thereby, the high-speed data search functionin reproducing can be realized.

Further, in the hierarchical coding system as described above, since thedata length of the distinction code for forming a picture, which iscomposed of the above division determination flag outputted from thecoders 51 to 55 of the hierarchical coding encoder unit 110Arespectively, (hereinafter these are called collectively inter-hierarchydata division determination code) at the decoding side, equals to thenumber of all of the blocks in each hierarchy data, the data length isto be fixed-length data respectively.

For this reason, in the transmission block 122, the inter-hierarchy datadivision determination coding the distinction code for forming a picturefor each hierarchy at the decoding side is arranged immediately afterthe uppermost hierarchy coded data D55. Thereby, even after the abovegenerated information quantity control has been performed, the data,which exists in the section of the uppermost hierarchical coded data D55and the inter-hierarchy data division determination code C2, is able tobe fixed-length as a whole.

In the variable-length data block 121, the fourth to the first hierarchydifference value coded data D54, D53, D52, D51 are sequentially arrangedand formed in this order, and the transmission block end code C3 forindicating the end of the transmission block 122 is added immediatelyafter the above variable-length data 121.

In the above structure, in this picture coding apparatus, with respectto the data which is generated at the hierarchical coding encoder unit110A, variable-length data is arranged for each frame after fixed-lengthdata, so that the transmission block 122 is formed and outputted to thetransmission line.

Accordingly, the decoding can be performed without making an error ofthe definition of the data in the fixed-length data block 120 at thedecoding side, even if an error is generated in any variable-lengthdata. Thereby, in this picture coding apparatus, the transmission datacan have robust characteristic for error.

Further, in the picture coding apparatus 110, when transmitting the datagenerated by the information quantity control method described theabove, the uppermost hierarchical coded data D55 is arranged immediatelyafter the transmission block identification code C1 and outputted, sothat in the case where the high-speed data search function is added atthe decoding side, it can access to the uppermost hierarchical codeddata D55 in short time after the transmission block identification codeC1 is detected.

According to the above structure, the coding of hierarchies having aplural of resolutions can be easily realized. Further, the totalgenerated information quantity of the transmission picture data which iscoded and outputted from the hierarchical coding encoder 110A, can bealmost equaled to the target value, thereby the coding in which thecompression efficiency does not lower can be realized. Further, thehierarchical coding in which the deterioration of picture quality islittle can be realized. Furthermore, the management of the generatedinformation quantity in the hierarchical coding can be simplifiedcomparing with the conventional one.

Further, the optimum threshold value can be set considering thecharacteristic of the picture signal data for each hierarchy and thevisual characteristics of human being, so that the subjective picturequality at the receiving side can be more improved comparing with thecase of setting a constant threshold value.

(3) Other Embodiments of Seventh Embodiment

(3-1) In the embodiment described above, such a case is described thatthe block activity value is determined based on the maximum value of thedifference value between the decoded data obtained for each block withrespect to the upper hierarchy data and the lower hierarchy data.However, the present invention is not to be limited to this, but thedetermination can be performed based on an average error, an absolutevalue sum, a standard deviation, an n-th power sum, or a data frequencywhich is larger than or equal to the threshold value.

(3-2) In the embodiments described above, such a case is described thatthe table frequency obtained for each hierarchy is utilized as it is.However, the present invention is not only limited to this, but theintegrating frequency table can be produced from the frequency table touse for calculation of the generated information quantity.

That is, after the frequency table is generated for each hierarchy, theaccumulative added value is obtained with respect to the blockfrequencies from the block activity value of higher order bit to eachblock activity values, and the respective accumulative added values iswritten to the address corresponding to each block activity value toproduce the integrating frequency table. Thereby, the frequencycorresponding to each block activity value becomes the integrated valueof the block frequency which has the value larger than or equal to theblock activity value.

By the integrating frequency table is produced previously in thismanner, it is not needed to calculate the block frequency integratedvalue corresponding to each threshold value, and the calculation of theblock frequency integrated value can be performed by merely reading outthe threshold value address of the memory, thereby a time forcalculation can be widely shortened.

(3-3) In the embodiments described above, such a case is described thatthe division/non-division of the block is determined by comparing thethreshold value which is set to the different value for each hierarchywith the block activity value. However, the present invention is notonly limited to this, but can be determined based on the comparisonresult that is compared the threshold value set to the different valuefor each hierarchy with the difference value of data betweenhierarchies.

(3-4) In the embodiments described above, such a case is described thatthe picture data is PCM coded at the coder. However, the presentinvention is not only limited to this, butbut can be applied the othercoding schemes, such as a orthogonal coding scheme.

(3-5) In the embodiments described above, such a case is described thata plurality of combinations of the threshold value of the frequencytable which is obtained for each hierarchy, are previously stored in theROM, and then the combination of the threshold value which is nearest tothe target value is obtained. However, the present invention is not onlylimited to this, but can set the combination independently for eachhierarchy.

(3-6) In the embodiments described above, such a case is described thatas to the lowermost hierarchy data, the mean value is obtained for eachunit of 2 lines×2 pixels, so that the picture data of the upperhierarchy is obtained. However, the present invention is not onlylimited to this, but the mean value can be obtained by the anothercombinations.

(4) As described above, according to the present invention, in a picturecoding apparatus for sequentially and recursively dividing a picturedata into plural hierarchy data having different resolution each otherand coding it, when the transmission data including respective codedhierarchy data is outputted to the specified transmission line, thevariable-length data is outputted to the transmission line after thefixed-length data by dividing the transmission data into thefixed-length data and the variable-length data for each specified unitforming a picture. Thereby, the contents of the fixed-length data can bedetected correctly when decoding it, even if error is generated in thevariable-length data, thereby a picture coding apparatus and datatransmitting method in which the transmission data can include therobust characteristic for error can be realized.

Industrial Applicability

A picture coding apparatus and a picture coding method of the presentinvention are applicable to a transmitter of the system which has amonitor having different resolutions at the receiving side, such as thetelevision conference system and the video on demand system.

We claim:
 1. A hierarchical picture coding apparatus for coding a plurality of hierarchical data having a plurality of different resolutions, comprising:a circuit for generating a plurality of levels of hierarchical data representative of pixel values in which each level represents a different resolution of an input picture signal; a circuit for detecting an activity representing spatial characteristics in a time domain of a predetermined block of hierarchical data representative of pixel values, controlling the division of a block of different hierarchy corresponding to said predetermined block based on said detected activity, and generating a flag showing the control of the division; and a circuit for coding said each hierarchical data.
 2. The hierarchical picture coding apparatus according to claim 1, wherein out said plurality of hierarchical data, each hierarchical data except for a hierarchical data having the lowest resolution is a hierarchical difference data which is the difference from a data having lower resolution.
 3. The hierarchical picture coding apparatus according to claim 2, wherein said hierarchical data generating circuit generates a hierarchical data having low resolution by averaging pixel values of a plurality of pixels in the block.
 4. The hierarchical picture coding apparatus according to claim 3, wherein each hierarchy difference data consists of the difference between (n-1)-number of hierarchical data and a hierarchical data having lower resolution than said (n-1)-number of hierarchical data.
 5. The hierarchical picture coding apparatus according to claim 1, wherein said division controlling circuit detects an activity of said each hierarchical data except for the hierarchical data having the lowest resolution.
 6. The hierarchical picture coding apparatus according to claim 1, wherein transmission of the data of the block to which said division is stopped is stopped.
 7. The hierarchical picture coding apparatus according to claim 1, wherein said input picture signal includes a plurality of signals having correlation for forming a picture from each other and said plurality of signals have a first signal and a second signal, and wherein said division controlling circuit detects an activity of said first signal and compares said activity with a threshold value so as to control the division of a block corresponding to said predetermined block in which said threshold value is determined based on said second signal.
 8. The hierarchical picture coding apparatus according to claim 7, wherein said first signal is a chrominance signal and said second signal is a luminance signal.
 9. A hierarchical picture coding method for coding a plurality of hierarchical data having a plurality of different resolutions, said method comprising the steps of:generating a plurality of levels of hierarchical data representative of pixel values in which each level represents a different resolution of an input picture signal; detecting an activity representing spatial characteristics in a time domain of a predetermined block of hierarchical data representative of pixel values, controlling the division of a block of different hierarchy corresponding to said predetermined block based on said detected activity, and generating a flag showing the control of the division; and coding said each hierarchical data.
 10. The hierarchical picture coding method according to claim 9, wherein out of said plurality of hierarchical data, each hierarchical data except for a hierarchical data having the lowest resolution is a hierarchical difference data which is the difference from a data having lower resolution.
 11. The hierarchical picture coding method according to claim 10, wherein the step of generating hierarchical data generates hierarchical data having low resolution by averaging pixel values of a plurality of pixels in the block.
 12. The hierarchical picture coding method according to claim 11, wherein each hierarchy difference data consists of the difference between (n-1)-number of hierarchical data and a hierarchical data having lower resolution than said (n-1)-number of hierarchical data.
 13. The hierarchical picture coding method according to claim 9, wherein the step of controlling the division detects an activity of said each hierarchical data except for the hierarchical data having the lowest resolution.
 14. The hierarchical picture coding method according to claim 9, wherein transmission of the data of the block to which said division is stopped is stopped.
 15. The hierarchical picture coding method according to claim 9, wherein said input picture signal includes a plurality of signals having correlation for forming a picture from each other and said plurality of signals have a first signal and a second signal, and wherein the step of controlling the division detects an activity of said first signal and compares said activity with a threshold value so as to control the division of a block corresponding to said predetermined block in which said threshold value is determined based on said second signal.
 16. The hierarchical picture coding method according to claim 15, wherein said first signal is a chrominance signal and said second signal is a luminance signal.
 17. A hierarchical picture transmission method for coding a plurality of hierarchical data having a plurality of different resolutions and transmitting the coded data, comprising the steps of:generating a plurality of levels of hierarchical data representative of pixel values in which each level represents a different resolution of an input picture signal; detecting an activity representing spatial characteristics in a time domain of a predetermined block of hierarchical data representative of pixel values, controlling the division of a block of different hierarchy corresponding to said predetermined block based on said detected activity, and generating a flag showing the control of the division of the block corresponding to said predetermined block; coding said each hierarchical data so as to generate the coded data; and transmitting said coded data and said flag.
 18. The hierarchical picture transmission method according to claim 17, wherein out of said plurality of hierarchical data, each hierarchical data except for a hierarchical data having the lowest resolution is a hierarchical difference data which is the difference from a data having lower resolution.
 19. The hierarchical picture transmission method according to claim 18, wherein the step of generating hierarchical data generates hierarchical data having low resolution by averaging pixel values of a plurality of pixels in the block.
 20. The hierarchical picture transmission method according to claim 19, wherein each hierarchy difference data consists of the difference between (n-1)-number of hierarchical data and a hierarchical data having lower resolution than said (n-1)-number of hierarchical data.
 21. The hierarchical picture transmission method according to claim 17, wherein the step of controlling the division detects an activity of said each hierarchical data except for the hierarchical data having the lowest resolution.
 22. The hierarchical picture transmission method according to claim 17, wherein transmission of the data of the block to which said division is stopped is stopped.
 23. The hierarchical picture transmission method according to claim 17, wherein said input picture signal includes a plurality of signals having correlation for forming a picture from each other and said plurality of signals have a first signal and a second signal, and wherein the step of controlling the division detects an activity of said first signal and compares said activity with a threshold value so as to control the division of a block corresponding to said predetermined block in which said threshold value is determined based on said second signal.
 24. The hierarchical picture transmission method according to claim 23, wherein said first signal is a chrominance signal and said second signal is a luminance signal.
 25. A hierarchical picture decoding apparatus for decoding coded hierarchical data, wherein said coded hierarchical data is obtained by coding a plurality of levels of hierarchical data representative of pixel values in which each level represents a different resolution, said hierarchical picture decoding apparatus comprising:a circuit for receiving said coded hierarchical data and a flag showing the control of a division of a block of different hierarchy corresponding to a predetermined block of hierarchical data representative of pixel values, in which the division of the block had been controlled during a coding operation based on a detected activity representative of spatial characteristics in a time domain of the predetermined block of hierarchical data; a circuit for decoding said coded hierarchical data; and a circuit for generating hierarchical data decoded based on the information on said flag.
 26. The hierarchical picture decoding apparatus according to claim 25, wherein out of said plurality of hierarchical data, each hierarchical data except for the hierarchical data having the lowest resolution is a hierarchy difference data which is the difference from a data having lower resolution, and wherein said hierarchical picture decoding apparatus further comprises a circuit for generating decoded hierarchical data and hierarchical data restored from decoded hierarchical data which has lower resolution.
 27. The hierarchical picture decoding apparatus according to claim 26, wherein said hierarchical data is generated by averaging pixel values of a plurality of pixels in a block of hierarchical data having higher resolution.
 28. The hierarchical picture decoding apparatus according to claim 27, wherein each hierarchy difference data consists of the difference between (n-1)-number of hierarchical data and a hierarchical data having lower resolution than said (n-1)-number of hierarchical data, and wherein residual hierarchical data are generated by arithmetic operations by said (n-1)-number of hierarchical data and said hierarchical data having lower resolution than said (n-1)-number of hierarchical data.
 29. A hierarchical picture decoding method for decoding coded hierarchical data, wherein said coded hierarchical data is obtained by coding a plurality of levels of hierarchical data representative of pixel values in which each level represents a different resolution, said hierarchical picture decoding method comprising the steps of:receiving said coded hierarchical data and a flag showing the control of a division of a block of different hierarchy corresponding to a predetermined block of hierarchical data representative of pixel values, in which the division of the block had been controlled during a coding operation based on a detected activity representative of spatial characteristics in a time domain of the predetermined block of hierarchical data; decoding said coded hierarchical data; and generating hierarchical data decoded based on the information on said flag.
 30. The hierarchical picture decoding method according to claim 29, wherein out of said plurality of hierarchical data, each hierarchical data except for the hierarchical data having the lowest resolution is a hierarchy difference data which is the difference from a data having lower resolution, and wherein said hierarchical picture decoding method further comprises the step of generating decoded hierarchical data and hierarchical data restored from decoded hierarchical data which has lower resolution.
 31. The hierarchical picture decoding method according to claim 30, wherein said hierarchical data is generated by averaging pixel values of a plurality of pixels in a block of hierarchical data having higher resolution.
 32. The hierarchical picture decoding method according to claim 31, wherein each hierarchy difference data consists of the difference between (n-1)-number of hierarchical data and a hierarchical data having lower resolution than said (n-1)-number of hierarchical data, and wherein residual hierarchical data are generated by the arithmetic operations by said (n-1)-number of hierarchical data and said hierarchical data having lower resolution than said (n-1)-number of hierarchical data.
 33. The hierarchical picture coding apparatus according to claim 1, wherein said hierarchical data generating circuit generates hierarchical data having a low resolution and (n-1)-number of hierarchical data having a resolution higher than said low resolution.
 34. The hierarchical picture coding method according to claim 9, wherein the generating step generates hierarchical data having a low resolution and (n-1)-number of hierarchical data having a resolution higher than said low resolution.
 35. The hierarchical picture transmission method according to claim 17, wherein the generating step generates hierarchical data having a low resolution and (n-1)-number of hierarchical data having a resolution higher than said low resolution. 